Charles A. Spencer's Trunnion Model Microscope c. 1855 

Charles A. Spencer's Trunnion Model Microscope c. 1855

Charles A. Spencer's Trunnion Model Microscope c. 1855

Charles A. Spencer's Trunnion Model Microscope c. 1855

From Carpenter's The Microscope and its Revelations, first American edition, 1855.

Mr. Charles A. Spencer of Canastota, New York, has manufactured a microscope of great excellence, the objectives of which will bear comparison with the best of foreign construction. His common angle of aperture for 1/4 inch objectives is 135 degrees; for 1/8 inch, 170 degress, and for 1/12 and 1/16 inch, 176 degrees. This. is believed to be the largest angle ever given to an object-glass, and for sharpness of definition and power of penetration, they are unexcelled by any of foreign make.

To Mr. Spencer is due the credit of having first resolved, with lenses of his own construction, the fine markings on the Navicular Spencerii and Grammatophora Subtilissima: these minute shells have since been adopted by microscopists as test-objects for the highest powers. The Navicula Spencerii, will exhibit one set of lines with Mr. Spencer's 1/4 th-inch object-glass: both sets with the 1/8 th-inch. The Glrammatophora Subtilissima is a good test for a 1/12 th or 1/16 th.

Of several microscopes made by Mr. Spencer, two or three only will be here noticed. His first-class or best instrument is mounted on trunnions, and embraces all the acknowledged improvements, in form and stage, whereby the greatest steadiness and freedom from tremor are secured. The price of this instrument with all the accessories and a full set of object-glasses will approach $350 (Fig, 426)


See the article An Early American Microscope, Proceedings of the American Microscopical Society, vol. 14, No. 3, Fifteenth Annual Meeting. Part III (Jul., 1893), pp. 156-158

charles spencer trunnion microscope

Charles A. Spencer (1813-1881), America's first microscope maker,

The following was extracted from The National Cyclopedia of American Biography, vol. XIII, 1906.

SPENCER, Charles Achilles, lensmaker, was born at Lenox, Madison co., N. Y., Sept. 13, 1813, son of Gen. Ichabod Smith and Mary (Pierson) Spencer, and a descendant of Thomas Spencer, the first of the family in America. The line is traced through Thomas's son Thomas, through his son Samuel, his son Thomas, his son Eliphalet, and his son Eliphalet, the father of Ichabod Smith Spencer. The last named was an officer in the war of 1812. The son was educated at Cazenovia Academy, Hobart College, and Hamilton College. He displayed his natural aptitude at a very early age, making his own optical glass when only twelve years old. In 1838 he announced himself as a manufacturer of telescopes and microscopes, locating his workshop at Canastota, N. Y., and here, in spite of busmess reversals he continued to devote himself to the perfection of the achromatic telescope and microscope, later becoming the pioneer in developing the possibilities of lensmakmg as applied to the microscope. Ten years later (1848) there issued from this little shop at Canastota lenses that mystified both English and French microscopists, chiefly because of their great resolving power. He had succeeded in making the microscope objectives so effective as to accomplish results in " definition " before unknown, surpassing the efforts of the best European opticians and upsetting their claim that they had obtained the largest angular pencil of light that could be passed through a microscope object glass. He had proved by actual construction that the angle of aperture in these higher power objectives could be greatly increased, and with it their defining and resolving powers. The English makers charged Mr. Spencer with the I knowledge of some mode of working glass as yet unknown to other opticians, and while this was partly true, his chief success was due to his tact in figuring the lenses so as to balance the aberrations, a process so delicate that it would have availed no one not possessed of the same skill to copy curves. From this time forward Mr. Spencer kept steadily in advance of foreign opticians as to angle of aperture; and his microscopical objectives were pronounced the best in the world. In the fall of 1873 a disastrous fire broke out in Canastota, destroying his shop with nearly all his tools and machinery (the accumulation of many years), together with a large amount of finished and unfinished work. Crippled, but not disheartened, he continued his work under difficulties, and in 1875 entered the employ of the Geneva Optical Works, Geneva, N. Y., where he worked for two years. During 1854-56 his business was conducted under the firm name of Spencer & Eaton, his partner being A. K. Eaton, and in 1877 he started the firm of C. A. Spencer & Sons, with his sons Herbert R. and Clarence Leslie Spencer, and Major O. T. May, his son-in-law. This association lasted for three years, when the health of Mr. Spencer, Sr., failed to such an extent that he gave up active work. On Aug. 10, 1881, Charles A. Spencer was elected one of the first honorary members of the American Society of Microscopists. He was married July 10, 1838, to Mary Morris, daughter of Lonson and Hannah Stilwell, of Manlius, N. Y., and had six children. He died at Geneva, N. Y., Sept. 28, 1881.


For an additional discussion of the life and work of Charles A. Spencer (1813-1881), America's first microscope maker, see Three American Microscope Builders published by the American Optical Company 1945.


This microscope shown on this page, while unsigned, is an example of Spencer's Trunnion microscope.  When originally found, this important and rare American microscope had been converted to a lamp. The lamp components have now been removed and the microscope has been restored. The mirror, condenser, and slide carrier are replacements.

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