William Henry Pratt, 1840 - ca. 1910

by Brian Stevenson
last updated September, 2019

William H. Pratt was an amateur microscopist who produced a good number of quality slides during the 1880s-1890s (Figure 1). Pratt worked as a time clerk in a factory in Taunton, Massachusetts, USA. By the mid-1880s, he was an avid slide-maker, with a particular interest in diatoms (Figure 2). Pratt was probably a member of the local Taunton Microscopical Society. He actively exchanged slides with other microscopists throughout the US, by publishing offers in popular magazines, by sending examples to members of other microscopical clubs and to editors of science magazines, and by providing mounts for sharing through the American Monthly Microscopical Journal’s “Postal Club”.

Figure 1. Three ca. 1890 microscopes slides that were made by W.H. Pratt.


Figure 2. Six arranged Aulacodiscus camberi diatoms from Peruvian guano, prepared ca. 1890 by W.H. Pratt (see Figure 1).


William H. Pratt was born in January, 1840, evidently the eldest child of Henry and Ann M. Pratt. Henry was a “printer”, according to census records. Four other children followed William, three girls, then a boy.

The 1870 census showed William living with his parents and siblings, and working as a “time keeper”. Further records clarify that he was an accounting clerk in a factory.

He married on October 19, 1870, to Ruth Richardson. The had one child, Herman, born in 1875.

The earliest record that I found about Pratt’s interest in microscopy is an 1887 report from the San Francisco Microscopical Society: “William Norris stated that several series of interesting slides had been received by him, which he would turn over to the Society. The first set was composed of diatoms collected and mounted in Australia, by Dr. Thomas Porter, and comprised many rare and beautiful forms. The second lot was from Wm. H. Pratt, Taunton, Mass., and the third from Gerald Stuart, F.R.M.S., London”. For Pratt to have sent examples of his slides across the country implies that he was already a competent mounter who could expect to impress Norris and other San Francisco microscopists, and would likely receive some slides in return.

In 1890, Pratt donated a slide of “diatoms from Buzzard’s Bay” to the American Monthly Microscopical Journal’s Postal Club (Figure 3). This operated on the same model as England’s Postal Microscopical Society, in which boxes of a half-dozen slides were assembled from volunteer preparers, then the boxes were posted to members in a circuit. Each member would have a few days to examine the slides, make notes then pass them along to the next person in the circuit. Pratt’s 1890 preparation was “characterized as a very fine mount”.

An 1891 advertisement in The Microscopist offered to exchange “first class diatom slides” (Figure 4).

Another attempt to attract exchanges occurred in 1892, when Pratt sent some of his slides to The American Monthly Microscopical Journal. They announced: “Arranged Diatoms - These always afford entertainment. W.H. Pratt, of Taunton, Mass., has made some nice slides from American diatoms”.

The 1898 Naturalists’ Directory noted that “Pratt, Wm. H., 49 Clifford St., Taunton, Mass.” was interested in diatoms and microscopy.

I did not find a record of when W.H. Pratt died. He was listed in the 1909 Taunton City Directory, when he would have been 70 years old, but has not been found in the 1910 US census.

Figure 3. List of the 6 slides that were included in an 1890 sharing box from American Monthly Microscopical Journal’s Postal Club. Note that two other colleagues from Taunton also provided mounts for this box, A.B. Hervey and F.A. Hubbard. Mr. Hubbard was the Secretary of the Taunton Microscopical Society. Ella Drury, a professional microscope slide-maker, also provided a slide to this box - an illustrated essay on Drury’s life and works is published on this site.


Figure 4. An 1891 exchange offer from W.H. Pratt, offering books for sale and diatom slides for exchange. From “The Microscope”.



The American Monthly Microscopical Journal (1890) Report of Postal Club boxes, Vol. 11, page 10

The American Monthly Microscopical Journal (1892) Note of the receipt of slides from W.H. Pratt, Vol. 13, page 125

Marriage record of William H. Pratt and Ruth Richardson (1870) accessed through ancestry.com

The Microscope (1887) Report from the San Francisco Microscopical Society, Vol. 9, page 54

The Microscope (1891) Exchange offer from William H. Pratt, Vol. 11, page 6

The Microscope (1893) List of microscopical societies: Taunton Microscopical Society, Vol. 12, page 120

The Naturalists’ Directory (1898) “Pratt, Wm. H., 49 Clifford St., Taunton, Mass. Diatoms, Mic. C. Ex?

Taunton Massachusetts City Directory (1909) page 266

U.S. census and other records, accessed through ancestry.com