Royal Sibley Warren, 1822 - 1896

by Brian Stevenson
last updated January, 2021

Dr. R.S. Warren was a physician and amateur microscopist, who lived in Waltham, Massachusetts (near Boston). He was particularly interested in diatoms, wrote of methods to clean and prepare natural samples of diatomaceae, and prepared his own microscope slides.

During the late 1870s, he produced and sold slides with attractive labels and handwriting (Figure 1). These were primarily of diatoms, but also including other, similar items such as polycystina. Warren probably made retail slides for only a few years, between 1877 and ca. 1880. They are not encountered very often nowadays.

Figure 1. Microscope slides that were prepared by R.S. Warren. Most of his known slide material came from bodies of water near Waltham or other points in the northeastern US, as with the top slide of diatoms from Annisquam, Massachusetts. He appears to have corresponded widely, however. For example, he published a request for correspondence in the 1878 “Bulletin de la Fédération des Sociétés d'Horticulture de Belgique” (Belgium).


Figure 2. An 1877 announcement that appeared in “The American Naturalist”. The Isles of Shoals are located off the coasts of New Hampshire and Maine, USA, not far from Warren’s home in Massachusetts.


Royal Sibley Warren was born on September 12, 1822 in Alstead, New Hampshire. He was the eldest of eight children of Emery & Parla Warren. Royal attended Harvard Medical College, and earned his M.D. in 1846. He then settled in Waltham, and practiced medicine until ca. 1881.

I have not found records of Warren joining any microscope societies. Yet, he clearly communicated with other microscope enthusiasts, and exchanged specimens. For example, the June 14, 1871, minutes of the Boston Society of Natural History reported that, “Mr. Stodder exhibited a slide containing Stauroneis Stodderii Greenleaf, from Lyman's Pond, Waltham, collected by Dr. Warren, a diatom which has not before been found outside of New Hampshire and Maine”. The exhibitor was Charles Stodder (1809-1884), manager of the Boston Optical Works, who distributed R.B. Tolles’ microscopes and other items (Figure 3). Warren later sold his microscope slides through Stodder (Figure 2).

Slide-makers often sent free samples of their wares to societies, in hopes of drumming up business. Warren also took that approach, as noted in the minutes of the November 7, 1878 meeting of the San Francisco Microscopical Society, “Dr. R.S. Warren, of Waltham, Mass., sent a box of sixteen slides of diatoms and some vials of material ready for mounting. All the slides are from famous localities, and contain interesting species - Navicula rhomboides, Coscinodiscus complexus, etc. A vote of thanks was given Dr. Warren for his kindness”. Details of Warren’s unmounted material were later provided by member William Ashburner, who wrote that diatoms from “Meads’ Pond and Lily Pond (Waltham, Massachusetts), Isles of Shoals, and Patuxent River, N.J. … were cleaned by Dr. R.S. Warren of Waltham, Mass., I merely mounted them”.

At the time of the 1880 US census, Warren was still working as a physician in Waltham, living with his wife, Susan, and four adult children (and two servants). Within the next year or two, Royal, Susan and two daughters moved to Colorado Springs, Colorado. The 1885 Colorado census listed him as being retired.

In early 1882, Warren published what appears to be his only significant paper on microscopy. “The preparation of diatoms” provides extensive, detailed instructions on methods of cleaning diatoms from all sorts of sources, including mud, sand, and fossil rocks. He signed the piece with his address in Colorado Springs. Warren’s article was widely cited, and large parts were reproduced in The Journal of the Royal Microscopical Society. The entire article is reprinted at the end of this essay, below Figure 4.

Shortly after Warren’s article was published, Frederick Kitton wrote to The American Monthly Microscopical Journal, complaining that Warren’s methods were essentially the same as Kitton had previously published in English magazines. Warren responded, “Having been absent in the mountains, I did not see, till the latter part of last month, the reply of Mr. Fred. Kitton, Honorary F.R.M.S., in the August number of the Journal, to my article on ‘The Preparation of Diatoms’, published in the June number. Though I had not unfrequently seen the Science Gossip, I had never met with Mr. Kitton's articles, nor heard of them till I saw his reply. My article was actually written about five years ago, and I then showed it to Mr. Charles Stodder, of Boston, Mass., well known to microscopists, who advised me to offer it for publication. I did not, however, and it laid among my papers till I took it up last March. With slight revision, it is the same as I wrote five years ago. Previous to 1877, I, in correspondence, and verbally, related the process as I have described it in my article, and I have done so since 1877. After reading Mr. Kitton's reply, I wrote to Mr. Stodder; he looked up Mr. Kitton's articles, and he writes me (he had never seen them before) that Mr. Kitton's description of the process is, indeed, very like mine. I can only say, this is coincidence. Had I known of Mr. Kitton's articles I might not have written upon the subject; or, had I written, I would have given him full credit. My purpose in offering my paper for publication was to present a simple, clear, concise account of the process from beginning to end, for large quantities of material as well as small, of the preparation of diatoms, such as I had not found in books or science publications, and such as I thought most of those, beginners especially, interested in the study of these beautiful objects, had not found. The claim to originality lay especially in the extended mode of getting rid of the sand. The chemicals I knew had been used before, if not in the same order”. The journal’s editor added, “A previous communication from Mr. Stodder confirms the above. Mr. Stodder writes: ‘I was surprised by the resemblances’; the difference is ‘mostly in phraseology’. This is only one of many curious coincidences which abound in literature”. Judging from the responses, and what is known of Warren’s character, it is reasonable to conclude that both Warren and Kitton had independently derived similar methods for diatom cleaning, based upon previously-published techniques from other diatomists.

No further information has been found to indicate that Warren continued his slide venture after moving to Colorado, suggesting a limited period of production, from 1877 until ca. 1880.

Dr. R.S. Warren died on February 13, 1896, in Colorado Springs.

Figure 3. An 1876 advertisement from Charles Stodder. He was the distributor for R.S. Warren’s microscope slides in 1877 (see Figure 2, above).


Figure 4. Polycystina from Barbados, mounted by R.S. Warren (Figure 1). Photographed with a C-mounted digital SLR camera, a 10x objective lens, and brightfield lighting with a light blue filter.


“The Preparation of Diatoms”, by R.S. Warren, M.D. (1882):

(note: in his follow-up letter, Warren defined "sub-plutonic" as “diatomaceous deposits found under beds of lava. They are found in regions where, in the geological changes, there have been great upheavals, subsidences, and volcanic action. They are hard from the heat of the lava at the time it overflowed the deposits”.

Directions for the preparation of diatoms are rather meagre in books. Those given by Pritchard; Dr. A. Mead Edwards in his work on the "Natural History of the Diatomaceae", Dr. Christopher Johnson, of Baltimore, in the Lens, Oct, 1872, and others, are good as far as they go. Cleaning is effectually accomplished by their processes, but their directions for the separation of the diatoms from the sand and broken diatoms are insufficient.

The process of preparing diatoms is simple, but requires great care, time, and patience. When the gathering is pure, as in filaments, or on algae, the process is easy; but when the gathering is in the mud of rivers, lakes, and ponds, or in the mud of marshes and harbors, in which there is more or less organic matter, and in lacustrine (sub-peat), sedimentary, sub-plutonic and fossil deposits, it is generally toilsome, tedious, and often difficult.

The chemicals used are carbonate of soda, liquor potassa (note: dilute potassium hydroxide in water), muriatic, nitric and sulphuric acids, bichromate of potash, chlorate of potash, and water of ammonia. The apparatus consists of glass beakers of various sizes, bottles, small and large, mostly widemouth, evaporating dishes, rubber tubing for syphons of one-eighth inch to one-quarter inch calibre, glass rods, or thick narrow strips of glass for stirring, glass slides, glass dipping tubes, filter-paper, funnels, and a chemist's retort-stand.

I have found the best commercial acids sufficiently good; if either need be chemically pure it should be the sulphuric. All the water used in the preparation of diatoms should be distilled or filtered, that there be no admixture of diatoms foreign to any material. For the same reason, the beakers, bottles and dipping tubes should be thoroughly cleansed after use, as diatoms will adhere to them unless great care is taken. I filter water through two thicknesses of druggists' filter paper, a piece of thin muslin being placed between them at the point of the filter to prevent easy rupture at that spot. Another desirable effect of filtering the water used, is that it is thus rid of much organic and other matter, and is made to practically answer the purposes of distilled water; besides, the latter is not easily obtained in large quantities, and is expensive. In this article, when water is mentioned, filtered water is to be understood.

The process of preparing diatoms varies somewhat according as the material may be mud, lacustrine, sedimentary, sub-plutonic, or fossil deposits. I will first describe the treatment of fresh, mud material, and will here say that many of my manipulations are derived from directions given by the authors above mentioned, but some are peculiarly my own.

Having a quantity of mud material, if in no haste, I put it into a widemouth bottle, and wash it repeatedly, allowing sufficient time for the material to settle after each washing, until it finally settles, leaving the water nearly or quite clear. The time required for the material to settle depends upon the forms in it, the quantity, and the size of the bottle. This is ascertained by examining some of the unsettled portion taken from just above the deposit with a dipping tube. A few drops of this evaporated on a slide and examined under a microscope will tell whether it contains anything more than organic matter. In this way can be ascertained the time required for the material to settle before draining off the water. The draining is done with the rubber tube used as a syphon. Having thoroughly washed the material, it is boiled for a short time in a solution of carbonate of soda (washing soda), about an ounce to the pint of water, in a glass beaker, then washed as before, till all the alkaline odor and taste have disappeared. This boiling in a solution of carbonate of soda destroys considerable of the organic matter, and in a measure cleans the diatoms. I have sometimes used, very carefully, with good effect, weak liquor potassa instead of carbonate of soda. The material is then ready for the acids. If in haste, I at once boil the material in a solution of carbonate of soda, or even dispense with this and treat it with the acids. But the washings and boiling in the solution of carbonate of soda remove a large quantity of organic matter and save acids.

When ready for the acids, I shake the material well in water, pour a certain quantity into a beaker, allow it to settle, and drain off the unsettled portion. I then add muriatic acid in about the following quantity: If the material occupies half an inch in depth, I add one-quarter to one-half an inch in depth of the acid. I then add one-third to one-half as much nitric acid, and stir the whole with a glass rod, or a strip of glass, when, placing the beaker on one of the rings of the retort-stand, on which has been fastened a piece of wire gauze to prevent the flame of the lamp from coming in direct contact with the beaker, the material is boiled for a few minutes, perhaps, seldom ten, and while boiling, finely powdered chlorate of potash, or finely powdered bichromate of potash, is slowly added till effervescence nearly or quite ceases, but the quantity used is much a matter of judgment. A good deal of effervescence ensues, and the beaker may be overflowed if not closely watched. The acids dissolve the salts of lime and other substances which may be in the material, and the chlorate and bichromate of potash combined with the acids destroy the organic matter by oxidation. After it has cooled, the material is washed free of the acids and the water drained off. It is then boiled in sulphuric acid, using nearly the same quantity as of the mixture of muriatic and nitric acids. While boiling, chlorate of potash, or the bichromate of potash in fine powder, is slowly added. If bichromate of potash is used, a few drops of muriatic is added. Generally the material turns pretty white; sometimes it will not. As with muriatic and nitric acids, a good deal of effervescence ensues, and the same watchfulness is necessary. Never add chlorate of potash to cold sulphuric acid or there will be explosion. It is safe to carefully add it in fine powder to boiling sulphuric acid. I prefer chlorate of potash in the whole process. I will remark here in regard to the use of the acids, that I have used them in various ways. I have first boiled the material respectively in sulphuric, muriatic and nitric acids, and in combination, and I have settled upon the above process of first boiling it in a mixture of muriatic and nitric acids, and then in sulphuric acid; I have found this to answer with all material, whether mud, lacustrine, sedimentary, sub-plutonic, or fossil.

After the boiling in sulphuric acid, the material is transferred to a wide-mouth bottle and repeatedly washed. After the material is freed of the acid, the light, broken portion of the material will remain suspended in the water above the settled portion. This is drained off by means of the rubber tubing, water is added, the material is shaken, allowed to settle, the floating matter drained off, and this is repeated till nothing remains but diatoms mixed with sand. If, however, flocculent matter should remain, and this can be ascertained with the microscope, it may be broken up and disposed of by means of common water of ammonia -concentrated water of ammonia one part, water two parts, by measure - and further washing. The ammonia should be carefully used as there is danger of injuring delicate forms by its use. If, for instance, there be a quarter of an inch depth of material in an eight-ounce bottle, not more than half an ounce, by measure, of the ammonia should be used. The material is well shaken in this for three or four minutes, the bottle then filled with water and the washing continued till the material is freed of all the flocculent matter. It is surprising, sometimes, to see the quantity of this.

We now have the diatoms mixed with fine sand. How are we to get rid of the latter? If there happens to be coarse sand in the fresh material, we may get rid of it by repeated settlings and decantations before boiling; and should some remain at the last washings after the boilings, it may be disposed of in the same way. But it is different with the fine sand. Graduated settlings and decantations have been advised; but these are insufficient, as, despite all care, more or less of light silt will float with the light forms of diatoms, and the heavy diatoms will fall to the bottom with the heavy sand. Whirling in an evaporating dish, has been advised, but this is insufficient. I have found no method better than the one I have used for several years, and which I have never seen described or hinted, except in regard to whirling. A few years ago, Mr. E. Samuels of Boston, Mass., told me he had used a method similar in some respects.

If the material contains the lighter forms only, I first use whirling force as follows: I take an evaporating dish of a size according to the quantity of material, and fasten it on the wheel of my turn-table by means of a narrow rubber band passed over it and under the wheel. The material is diffused in five or six times its bulk of water. An empty, wide-mouth bottle is near the turn-table and should have a capacity of two or three times the quantity of diffused material. Shaking the material well, I fill the evaporating dish about two-thirds, and then whirl it with considerable rapidity till I think the sand has mostly settled at the bottom of the dish, for the whirling motion causes it to fall. I then pour off the unsettled portion into the empty bottle and add more of the material to the sand and diatoms remaining in the dish, and stir with a narrow strip of glass, the whirling is repeated; and so on with all the material. When this has been done, water is added to the portion in the dish and the process continued till no diatoms remain in the sand. To ascertain this, the dipping-tube, again comes into use. The material is treated in this way several times, till no sand can be obtained by it. If the material contains heavy diatoms like the large pinnularias, Triceratium favus, and heavy disk-forms, the whirling process cannot well be used, for these heavy forms fall to the bottom of the dish with the sand.

After the above process is ended, I proceed as follows, and this is, in most cases, the only method used after the boiling and washings. I have a slide of polished glass 3 1/2 inches by 4 1/2 inches; a smooth block of wood 4 inches by 5 or 6 inches, and 3 inches thick; two wide-mouth bottles of four to six ounces capacity, with thin, projecting lips, one empty, the other filled with the material thinly diffused in water; several pieces of considerable size of old worn cotton cloth, and, for I like it best, a clean linen pocket-handkerchief, and a small table. The table I place beside my wash-bowl which is supplied with water - not filtered in this instance - through a pipe and faucet, and on it are arranged my bottles, block and cloths. I place the glass slide on the block, taking care that the latter is level, and, well shaking the material, pour a little of it on the slide, and then quickly pour it off, tipping the slide so that the material will flow off from a corner of it into the empty bottle. The diatoms float off into the bottle, and the sand adheres to the slide. The slide is then washed by letting water upon it from the faucet, then wiped as well as may be with one of the large pieces of cloth, and then the surface to be used is wiped with the linen handkerchief. This last wiping dries the surface thoroughly, and removes any little shreds of cotton, which may have adhered to it from the cloth. Care is taken that none adhere. In this way the material is all worked over and this treatment has to be repeated perhaps many times before the material is sufficiently rid of the sand. It may be that before this is accomplished, the sand and diatoms will cling together on the slide, causing considerable loss of the latter. This is owing to little particles of matter getting into the material from the cloths, or from the air, and cannot be prevented. As soon as this clinging is detected, which is easily done by occasionally examining the slide under the microscope, first drying it after pouring off the material, the latter should be boiled for a minute in sulphuric acid, to which is added a little chlorate of potash while boiling. Of course the diffused material is poured into a beaker, allowed to settle, and the water drained off. It is then washed and the treatment continued. When the material is at last freed of sand, it is boiled a last time in sulphuric acid, chlorate of potash being used as before. It is then thoroughly washed and properly diffused in dilute alcohol for mounting. The alcohol should be filtered as well as the water.

In this last process some of the diatoms will adhere to the slide, but this is of little consequence if there be plenty of material. As the cloths get pretty wet, as they will, they should be exchanged for dry ones.

Such is the treatment of fresh-mud material. Lacustrine (sub-peat), sedimentary deposits and guano, are treated in the same way.

The treatment of hard, sub-plutonic and fossil material is somewhat different. This material is often very hard and has to be reduced to powder. This is accomplished by boiling it in a solution of caustic potash -liquor potassa. This should be cautiously used, as too much boiling in it will injure the diatoms. Boiling in a strong solution of carbonate of soda will often accomplish the same end, though not so easily, but its use is safe. As soon as a portion of the material has fallen in powder, it should be poured into a large quantity of water, and the remaining lumps boiled in the solution of potash or of carbonate of soda; this is to be repeated till the whole has been reduced to powder. The treatment is then by acids, etc., as with fresh-mud material. Fresh-mud material should not be allowed to dry, as it is then very difficult to reduce it to powder. When dried hard, perhaps the best way is to first burn it in a crucible, or in an iron pan over a hot fire; the organic matter will be pretty well burned out of it, and it is reduced to powder.

There are generally, I may say always, many broken diatoms in subplutonic and fossil material. It is very desirable to get rid of these. It may be accomplished in a great measure by using the slide as for getting rid of sand. The broken diatoms adhere by their rough edges to the surface of the glass, whilst the whole diatoms float off; but more will be lost, perhaps, than when getting rid of sand in this way.

When the material is pure, as in filaments, or when attached to algae, it is boiled in the acids, very gently if the forms are delicate. The action of the acids, chlorate and bichromate of potash, and the washings remove all organic matter and leave the diatoms pure.



American Journal of Microscopy and Popular Science (1876) Advertisement from Charles Stodder, Vol. 1, November issue

American Journal of Microscopy and Popular Science (1879) Letter to the Editor: “A Correction. Ed. Am. Jour. Microscopy - In the report of the annual meeting of the San Francisco Microscopical Society, held January 13th, contained in your March number, p. 71, it is stated that I presented the Society with seven slides of diatoms, finely cleaned and mounted by myself, from Santa Monica, Richmond, Maryland, Meads’ Pond, and Lily Pond, (Waltham, Massachusetts,) Isles of Shoals, and Patuxent River, N.J.  The last four of the above were cleaned by Dr. R.S. Warren of Waltham, Mass., I merely mounted them. In justice to Dr. Warren, I should be much obliged if you would make the correction in your next issue. Wm. Ashburner”, Vol. 1, November issue

American Naturalist (1877) Announcement that slides by R.S. Warren were available from Charles Stodder, Vol. 11, page 188

Bulletin de la Fédération des Sociétés d'Horticulture de Belgique (1878) “Correspondence: Waltham, M. Dr. R.S. Warren (Diatomaeées)”, page 91

Journal of the Royal Microscopical Society (1882) Preparing diatoms, Series 2, Vol.  2, pages 707-708

Kitton, F. (1882) The preparation of diatoms, The American Monthly Microscopical Journal, Vol. 3, page 153

The Medical Register for New England (1888) “Warren, Royal S., Waltham - 1846. M.D. (Harv.)”, page 435

The Pacific Medical Journal (1878) Minutes of the November 7 meeting of the San Francisco Microscopical Society, Vol. 21, page 322

Proceedings of the Boston Society of Natural History (1871) Minutes of the June 14, meeting of the Section of Microscopy, Vol. 14, pages 304-305

The Record of Baptisms, Marriages and Death, and Admissions to the Church and Dismissals Therefrom, Transcribed from the Church Records in the Town of Dedham, Massachusetts, 1638-1845 (1888) “Children of Emery & Parla P. Warren, Royal Sibley, born Sept .12, 1822 …”, ed. by Don Gleason Hill, Dedham Historical Society, Dedham

US census and other public records, accessed through

Warren, R.S. (1882) The preparation of diatoms, The American Monthly Microscopical Journal, Vol. 3, pages 111-115

Warren, R.S. (1882) Cleaning diatoms - reply to Mr. Kitton, The American Monthly Microscopical Journal, Vol. 3, pages 225-226

Warren, R.S. grave marker,