Frederick Henry Lang, 1816 - 1892

by Brian Stevenson
last updated February, 2022

F.H. Lang was a member of the Royal Microscopical Society from 1861 until the end of his life, and President of the Reading Microscopical Society from the early 1860s until he moved to Dorset in 1875. He wrote authoritatively about preparing microscope slides, so it is likely that many of the surviving slides that bear his name were made by him (Figures 1-3).

Lang wrote two extensive articles on mounting diatoms that are readily followed and may be of benefit to modern microscopists. They are reproduced at the end of this historical essay.

Figure 1. Microscope slides with F.H. Lang's handwritten name. Many of his slides carry his name on oval labels. I am not aware of Lang having used typeset name labels. He very likely prepared all of these slides himself.


Figure 2. Dated 1864, a Lang slide of dry-mounted "Eggs of a red spider on expended cartridge", from Clifton (a suburb of Bristol). Lang attended the 1864 meeting of the British Association for the Advancement of Science, which was hosted by Bristol and Bath Societies, and may have acquired the specimen there. The "cartridge" would have been a quantity of gunpowder wrapped in thin paper, which was rammed down a rifle/musket barrel with a bullet on top. Firing the gun would expel both the bullet and the paper cartridge wrapper.


Figure 3. "Vertical section of canine of stoat", with F.H. Lang's handwritten name. He may have prepared this thinly-ground section himself, or it may have come from a colleague – handwriting comparisons are not conclusive.


Figure 4. Whole "Allantino viridis Saw Fly" (now Rhogogaster viridis) by a professional slide-maker (possibly Rev. John Thornton, 1808-1887) . Lang applied an oval paper label to the slide, and signed his name to indicate ownership.


Figure 5. Drawings made in 1865 by F.H. Lang of a testate amoeba he discovered and named Difflugia triangulata (now Nebela triangulate). From "The Transactions of the Microscopical Society of London".


Frederick Henry Lang was born on June 26, 1816 in the parish of Saint Marylebone, London, son of Robert and Maria Lang. Father Robert was a wealthy trader, with business ventures that included sugar plantations in Grenada and Guiana.

Frederick enlisted in the British Army on July 6, 1834. He was a Captain in the 34th (Cumberland) Regiment of Foot on December 24, 1846, when he married Helen Conyers in Corfu. She was the younger daughter of Major General Charles Edward Conyers, who was then on half-pay and serving as Commander and Inspecting Officer of Troops in the Ionian Islands.

Lang resigned in about 1850, and settled in Northam, Devon. His father had died in 1828, and his mother in 1846, and they evidently left a considerable estate to Frederick. The 1851 national census recorded Lang as a "fundholder", with he, Helen, and their two young children being served by a nurse, a nursemaid, a cook, a housemaid, and a houseman. The remainder of Lang's life was similarly luxurious.

On July 17, 1858, Lang was appointed Adjutant of the Royal Berkshire Militia. He was generally known by his Army rank of Captain. The Lang family thus moved to Reading, Berkshire.

Soon thereafter, Lang became involved with the Reading Microscopical Society. He served as President for many years, and quite possibly was a founding member. He was elected as a Fellow of the Microscopical Society of London (later the Royal Microscopical Society) on June 12, 1861.

Living only 40 miles from London, Lang attended at least some meeting of the Microscopical Society of London/RMS. In 1865, he published a letter in The Transactions of the Microscopical Society of London that indicated familiarity with "the annual soirées of the London Society".

Lang published a notable paper "On selecting and mounting diatoms" in 1870. He began by stating, "In the very last year of the late Dr. Arnott's life (note: diatomist George Walker-Arnott, 1799-1868), I heard him say that were he to commence a fresh collection of diatomaceae he would admit none but perfectly pure and unmixed gatherings into his cabinet. I was much struck with this observation at the time, but reflection convinced me that the longest life would not suffice for such an undertaking, as a pure gathering is the exception, and a mixed one the rule. The systematic diatomist must, therefore, be put to all sorts of straits, and the same gathering has to do duty in the cabinet as an example of various genera and species; and in many instances the particular species to be illustrated, if it is at all a rare one, is almost smothered by the commoner and more numerous ones." He followed this with detailed descriptions of methods for selecting and mounting individual diatoms. Lang's letter is reproduced in full at the end of this historical essay, as it may be of value to modern enthusiasts.

Soon afterwards, another amateur microscopist, Captain Rice D. Knight (ca. 1829 - 1885) wrote to The Transactions of the Royal Microscopical Society with reference to Lang's paper, bemoaning his difficulties in obtaining specimens of diatoms from beyond his neighborhood. Lang soon followed with detailed instructions of methods by which one could melt and dissolve the mountant of existing slides of mixed diatoms, then sort and mount them according to Lang's methods ("Another hint on selecting and mounting diatoms"). He also pointed out that this would be useful for restoring slides that had become damaged. This letter is also reproduced below.

Lang resigned from his position in the Royal Berkshire Militia in 1875, and was awarded an retirement allowance, the honorary rank of Major, and the right to continue to wear his uniform. He retired to Parkstone, Dorset, to live with Helen, three unmarried daughters, a married daughter and her young children, and, according to the 1881 census, a cook, a parlour maid, two housemaids, a nurse, and a coachman. The husband of the married daughter was an officer in the Royal Navy, and was presumably at sea at census time. Lang's two sons were also officers in the Army or Navy.

I did not find evidence of Lang joining a microscopical society in Dorset, nor of him writing further on the subject. He did, however, remain a Fellow of the Royal Microscopical Society for the remainder of his life.

Helen, his wife, died in 1884. Frederick Lang died on December 30, 1892, leaving an estate in excess of £25000.




"On Selecting and Mounting Diatoms", by Frederick H. Lang, 1870

Up to the present time a well cleaned but mixed slide of the diatomaceae from any particular locality has, as a general rule, been considered sufficient ; but though such slides are interesting, and in one sense instructive, as showing the prevalent genera and species abounding in a stated place, they are, in another point of view, unsatisfactory, and teach the beginner little. In the very last year of the late Dr. Arnott's life, I heard him say that were he to commence a fresh collection of diatomaceae he would admit none but perfectly pure and unmixed gatherings into his cabinet. I was much struck with this observation at the time, but reflection convinced me that the longest life would not suffice for such an undertaking, as a pure gathering is the exception, and a mixed one the rule. The systematic diatomist must, therefore, be put to all sorts of straits, and the same gathering has to do duty in the cabinet as an example of various genera and species; and in many instances the particular species to be illustrated, if it is at all a rare one, is almost smothered by the commoner and more numerous ones. This is of course a great drawback to any one commencing the study of these organisms, as he is confounded with the multiplicity of almost similar forms, and can only with doubt and difficulty identify the one he is searching for. But if pure gatherings of all species cannot be obtained, it is now comparatively easy to pick out those that are required from the general mass; and it is a matter of wonder to me that this has not been more generally attempted, for I am not aware of a single collection of the kind, with the exception of that which Eulenstein is now making for his subscribers. Selected diatoms of the more showy sort are occasionally to be obtained at the opticians, even arranged in patterns as pretty 'Oh law' objects for the microscope; but I would fain induce our members, and others also, to isolate and mount on separate slides every diatom, common or rare, that is to be procured in their own locality, or in gatherings from elsewhere; for if every one would set to work to do this, we should soon be in the possession of a complete series of really instructive slides of the diatomaceae.

The object of my paper this evening is not only to insist upon the advantages of this plan, but to render the task easier by giving you the benefit of my own experience, reaped through many failures, in selecting and mounting these exquisitely delicate and beautiful forms.

For a long time I had been content with mounting general gatherings, but having received from Liverpool some Californian shell cleanings. I was tired with the ambition of picking out the beautiful foreign forms abounding in the general dirt and debris, and, not having the slightest idea how to proceed, I consulted the well-known little work 'On Preparing and Mounting Microscopic Objects', by Mr. Davis. This, however, did not give the information required.

Left, then, to my own resources, I have found that the best implement for picking out diatoms is a finely-pointed badger's hair whipped on to a light handle, so that the hair does not protrude more than 1/8th in., thus insuring sufficient stiffness, whilst, undue elasticity avoided. If this is dipped into a weak solution of gum, and being allowed to dry, is then breathed upon, the most delicate form from a dried gathering may be taken up, and will remain on the hair if it is held steadily, whilst the slide containing the general gathering is shifted, and that on which it is to be placed substituted. On the latter, near the centre, which of course must be marked, has been placed a drop of fluid, to be hereafter described, and into this the hair is lowered, when the diatom adhering to it is immediately freed, and can then be pushed into position in the centre, and thus any number can be arranged as desired. It is preferable to mount all diatoms on the cover and not on the slip; the method of doing this is described farther on. In either case a few minutes exposure on the hot plate evaporates any moisture, when the collection is ready for the mounting process.

Here the beginner encounters two difficulties - the wave of balsam is apt to float away the diatoms, or should this luckily not be the case, they are often crushed by the contraction of the medium as it dries. Observing that Mr. Davis states that, to avoid the first cause of failure in mounting general gatherings, Professor Ryland adds a drop or two of gum to the last washing of his collection, I availed myself of the hint, modifying the plan to suit my own purpose. Of course, for selection, no gum must be mixed with the last washing, as it is imperative that the diatoms should be perfectly loose and free for lifting; but one or two drops of gum in a quarter of an ounce of distilled water makes a capital fluid, into which the selected forms may be dropped previously to their being pushed into place, and this is amply sufficient to fix them firmly. (footnote: A grain and a half of dry gum-arabic to an ounce of distilled water form the best solution for this purpose, though for the Campylodisci, Aulacodisci, and some species of Coscinodisci, &c., which rest on a small portion only of their surfaces, a little more gum is requisite to retain them in their places.)

A shallow cell formed of paper, card, or tea-lead will obviate the second cause of failure, but this necessitates the trouble and time of papering the slide, whilst Möller's thin glass cells are difficult to procure, and costly. Here I was for a long time at fault, but happening to make the acquaintance of Captain Haig, who is an adept at mounting diatoms, he kindly showed me that a ring of gold-size, if subjected to great and prolonged heat, becomes perfectly black and charred, and is then not affected by balsam, and thus forms the very cell I was searching for. Captain Haig burns these on the hot plate by means of a Bunsen burner, at a great expenditure of gas and much tedious watching, but I find the same result is obtained by giving the prepared slides to my cook to be placed in the oven when she is baking. He uses very thick balsam, but working, as I prefer, with that medium very much thinned with chloroform, it is just possible that even such cells may, in the-course of time, be acted upon by it; and so I have since hit upon the plan of forming my rings of gum-dammar dissolved in benzole. Of course I am aware that the chloroform of the balsam will affect these also, but this is of little consequence, as the one material is as transparent as the other, and should they entirely mix, the necessary thickness of medium to prevent crushing is gained.

I may here mention that a thin solution of gum-dammar is equally as good as balsam for mounting diatoms; it must, however, be filtered through blotting-paper to get rid of impurities in the gum. For this reason Mr. Tatem, in conjunction with whom I have been carrying on these experiments, objected to the gum-dammar cells, not being aware that it could be so easily filtered, and suggested that they should be formed of a solution of pure gum-arabic, which is not acted upon by balsam. We have both tried such cells, and find they answer admirably. Practically, however, I find it matters little whether the cell is formed of gum-arable or gum-dammar, and in either case the superfluous portion of the ring beyond the covering glass is easily cleaned off, if desired, in the usual manner, when it would be almost impossible for any one to tell that a cell had been employed. The pointed end of a small stick (an expended lucifer match will do) is better than a brush to form these ring-like cells, as it can be thrown away and a fresh one used on each occasion.

Some delicate diatoms are almost obliterated in balsam, and should be mounted dry. This is not such an easy task as it may appear, as such slides are apt to become spoiled by the penetration of damp, which eventually forms in beads of moisture on the inner surface of the covering-glass. Captain Haig for such purposes still uses his gold-size rings which in this case aге not completely charred, but are removed from the hot plate, whilst the point of a needle will still leave its impression on the ring as long as it is hot, but will not do so when it cools. By replacing the slide on the hot plate at the moment of mounting, the ring is once more softened and the cover applied and pressed down to insure adhesion. I have, however, found that the fumes from the heated gold-size are liable to form crystals which are as unsightly, if not so injurious, as the beads of moisture; and so I prefer using his charred ring, which I smear with my gam-dammar solution on which, whilst it is still slightly viscid, I press down the covering-glass; and afterwards, if the adhesion has been made perfect round the whole periphery, a finishing coat of asphalte or other varnish may be added, and thus all danger of damp or of crystals is avoided.

Captain Haig gave me two other most useful hints which he has most kindly allowed me to mention. Of course all diatoms should be mounted on the cover. To secure the correct centering of them, he forms on a glass slip, by means of the turn-table, а ring of gold size 3/8ths of an inch in diameter, the size of his covering glass, and within this a very minute one exactly in the centre. This is hardened by heat, as his cells are. On the outer ring, at equal distances, are placed three little bits of beeswax. The covering glass, on which it is intended to arrange the diatoms, is placed on this general mounting slip, and slightly pressed on the wax. Instead of distilled water, he places on the cover a very slight smear of glycerine, into which previously, as in the case of the water, a drop of gum may have been added. Into this the diatoms are dropped, and may then be pushed within the inner ring, and their perfect arrangement and centering are secured. The advantage of the glycerine over the water is that it is a greater solvent for freeing the diatoms from any extraneous dirt, and that it will remain moist for any length of lime. When the arrangement is completed, the covering glass is gently pushed off the three pieces of wax, and transferred from the slide to the hot plate, when in a few minutes the glycerine is evaporated. Put on another slide under the microscope, a drop of benzole is placed on the diatoms, and whilst they are being permeated by it, and all air displaced, a little balsam is dropped into the prepared cell, when the cover is seized by the forceps, reversed, and placed carefully on it, and the mounting is completed in less time than it has taken to tell the process.

I must state, however, that Mr. Tatem, whose slides of diatoms are almost absolutely perfect as to cleanliness and neatness of arrangement, prefers simple distilled water, with of course the necessary addition of gum, to the glycerine, which he considers messy. He uses a finely-pointed sable brush, instead of the badger's hair, both for selecting and arranging; for though, owing to the rapid evaporation of the water, the diatoms may become dry and fixed before they are exactly in position, a touch of the brush again moistens them, when they may be shifted as required. He also places his cover with the diatoms on the cell, which has been simply filled with chloroform, and then, placing the balsam at the edge, allows it to run in and replace the more volatile medium as it evaporates, thereby avoiding all chance of an entangled air-bubble. This process, however, must entail a good deal more trouble in cleaning off the superfluous balsam; and after mounting many dozens of slides after my plan I may fairly assert that I have never once been troubled by a persistent air-bubble; whilst a very little experience teaches the manipulator the exact quantity of balsam required for such very small cells, so that no after-cleaning is necessary, with the exception of washing the upper surface of the covering glass with a little soda and water. This, it may be remarked, does not affect the gum-dammar ring though it would the gum-arabic one, nor the balsam in which the diatoms are mounted; whereas, if spirit is used to clean off the slide, considerable danger is incurred lest the cover be shifted, whatever may be the nature of the cell, using as we do very fluid balsam.

Of course for the selection of the smaller diatoms a higher power than is afforded by a simple lens is requisite. Some persons can work with the compound microscope, though every movement is reversed by it; but for those who cannot do so, some kind of erecting microscope is necessary. Mr. Curteis, of Mr. Baker's firm, has kindly arranged for me such an instrument. It consists of his 'travelling or sea-side microscope', to which has been adapted a French erecting prism over the eye-piece, whilst above the circular glass stage is firmly fixed an oblong wooden one, giving sufficient rest for the hands and wrists of the manipulator. I cannot speak too highly of its practical use for the purposes I require. When thus employed as a dissecting microscope, the stage is in a horizontal, and the body in a vertical position, with the prism at almost a right angle; and thus the workman sits in a natural, unconstrained position, looking straight to his front, and the tedious and unhealthy stooping position entailed by the simple dissecting microscope is avoided. It is at the same time in its ordinary state, without the prism and extra stage a very handy and useful little instrument for the purposes it is intended for.

In conclusion, I will only remark that though perhaps none of us can hope to equal Möller's beautiful type-slide, with which we are so well acquainted, I do trust that the time is not far distant when the diatomists of this country will be able, each of them, to make type-slides of the prevailing species of their own localities, arranged according to some acknowledged synopsis; for thus alone can a sound knowledge, of these organisms be obtained, the vast number of synonyms be reduced order replace the present chaotic confusion, and the pursuit converted into a regular science.




"Another Hint on Selecting and Mounting Diatoms", by Frederick H. Lang, 1871.

My paper 'On Selecting and Mounting Diatoms', read to the members of the Reading Microscopical Society in October, 1870, and published in the December number of the 'Monthly Microscopical Journal,' has been, I have every reason to believe, of considerable use to amateur microscopists. In last April's number of the same Journal appeared a friendly notice of it in a letter from Capt. Knight, in which, acknowledging the advantage of making classified collections of diatoms, he speaks of the difficulty of procuring the material for so doing, and observes that professional mounters and opticians will only sell you their mixed gatherings, set, as a general rule, in balsam; though occasionally, but seldom, a dry mount may be obtained, when it is an easy matter to remove the cover and select the required forms. He does not, however, appear to think it possible to utilize for the purpose the balsam-mounted material, and I suspect others as well as myself have till now been of the same opinion. My friend Mr. Tatem has, however, turned his attention to the subject, and has discovered a very easy plan for picking out any desired forms from such slides for the purpose of remounting them. He has kindly communicated his method to me, and permitted me to publish it as an addendum to my former paper. Having both of us given it a fair trial we can confidently recommend the plan, which is as follows:

Place the balsam-mounted slide on the hot plate, and when it is sufficiently warmed tip over the cover by means of a needle; the diatoms will be either on it or the slide, it matters not which. Apply over them at once, whilst still on the hot plate, a drop of turpentine, remove the slide to the stage of the dissecting microscope, and add more turpentine. Have ready a clean slip of glass on which has been placed a drop of turpentine. In the case of large discoid and other forms, having applied plenty of turpentine, they can be easily transferred by means of a fine sable-hair brush from the original slide to the pool of turpentine on the clean one. In the case of finer forms it is better to place less turpentine on the original slide, collect the diatoms into a heap, allow the turpentine to dry a little, and then by a twist of the brush to transfer them en masse to the new slide. In either case, having got them there push them together and mop up the superfluous turpentine, and then, still under the dissecting microscope, slant the slide by placing a piece of folded paper under one end, and apply a little benzole either by means of a clean brush or glass rod immediately above them, that is, on the end of the slide that is raised, and allow it to float gradually over them, care being taken that it does not flow with too great a rush and carry away the diatoms with it. Repeat this process some half-dozen times, till the whole of the turpentine and balsam has been washed away, and till the valves are left dry and black after the benzole is evaporated. They can then be transferred in the usual way to any other slide, and even with greater ease than from an ordinary dry gathering. 1 may as well add that if gum has been used to fix the diatoms, it may be found that some of the valves, especially the discoid ones, remain obstinately adherent to the glass after the turpentine has been placed over them. In such a case, the process, as above detailed, must be carried out on the original slide, and then, after the benzole is thoroughly evaporated, water must be applied two or three times in the same way as the benzole for the purpose of washing away the gum and freeing the diatoms, which can then, when dried, be lifted one by one and transferred in the usual manner.

By this simple and easy method we can not only select from balsam-mounted gatherings any particular valves we may require, but we can reset any spoilt or unsatisfactory mounts of our own.





Birth and baptism record of Frederick Henry Lang (1816) Parish records of Saint Mary, Marylebone, accessed through

Bulletins and Other State Intelligence (1858) "County of Berks, Royal Berks Militia. Adjutant Frederick Henry Lang, late Captain in the 34th Regiment of Infantry, to serve with the rank of Captain. Dated 17th July, 1858", page 3690

England census and other records, accessed through

Knight, Rice D. (1871) A proposal as to diatoms, Transactions of the Royal Microscopical Society, Vol. 5, pages 190-193

Lang, Frederick H. (1865) Diagrams of microscopic objects, Transactions of the Microscopical Society of London, Vol. 13, pages 64-65

Lang, Frederick H. (1865) Beck's Treatise on the Microscope, Transactions of the Microscopical Society of London, Vol. 13, pages 228-229

Lang, Frederick H. (1865) A new Difflugia, Transactions of the Microscopical Society of London, Vol. 13, pages 285-286

Lang, Frederick H. (1870) On selecting and mounting diatoms, English Mechanic and World of Science, pages 270-271, reprinted from The Monthly Microscopical Journal

Lang, Frederick H. (1871) Another hint on selecting and mounting diatoms, Transactions of the Royal Microscopical Society, Vol. 5, pages 215-216

Mitchell, Edward A.D. (accessed February, 2022) The identification of Nebela and similar species with indications on their ecology and distribution,

Monthly Microscopical Journal (1874) Reading Microscopical Society, pages 181 and 296

Monthly Microscopical Journal (1875) "Reading Microscopical Society, October 12, 1875 - At this, the first meeting of the Society for the winter session, after the transaction of the usual business, and the reading of a letter from Major Lang, the following resolution, moved by Mr. J.G. Tatem, and seconded by Dr. Shettle, was unanimously passed: That this meeting receives with the deepest regret Major Lang's resignation of the office of President, which, from the very commencement of the Society, he has with so much courtesy, and profit to the members, kindly filled. That the members of the Society regret that the only return they can make for the frequent self-denial which their late President's regular attendance at the monthly meetings must have involved, and for his constant devotedness to the interests of the Society in every way, is to express their hearty and unanimous recognition of all the services he has so long rendered, for which they tender their best thanks; and they also indulge the hope that he will allow them to consider him honorary Vice-President and Corresponding member, which they trust they may for many years be permitted to do.", page306

Probate of the will of Frederick Henry Lang (1893) "Lang Frederic Henry of St. Katherine's Upper Parkstone Great Canford Dorset esquire major in Her Majesty's army died 30 December 1892 Probate London 18 February to Charles Edward Lang major in Her Majesty's army and Conyers Lang commander in Her Majesty's navy Effects £24350 19s 2d resworn March 1893 £25786 2s 9d", accessed through

Quarterly Journal of Microscopical Science (1861) Election of Fellows, Vol. 1, page 221

Royal Microscopical Society Charter and Bye-laws: List of Fellows (1892) "1861 – Lang, Major Frederick Henry, St, Katherine's, Parkstone, Dorset"

The Spectator (1847) Marriages: "On the 24th December, at Corfu, Frederick Henry Lang, Esq., Captain in the Thirty-fourth Regiment, son of the late Robert Lang, Esq., of Moor Park, Surrey, to Helen, second daughter of Major-General Conyers, C.B.", Vol. 20, page 31

The United Service Magazine (1875) "Royal Berks - Capt. and Adjt. Frederick Henry Lang resigns his commission, and is placed on a retired allowance, also is granted the Hon. rank of Major, and is permitted to continue to wear the uniform of the regiment on his retirement", Vol. 138, page 556