A POWERFUL MICROSCOPE.

Globe, Volume XX, Issue 1579, 12 March 1879, Page 4

A POWERFUL MICROSCOPE.

[From the N. Y. Times.l Dr. Ephraim Cutter, of Boston, whose name is familiar in scientific literature as that of a microscope enthusiast, exhibited last night, at the meeting of the New York Academy of Sciences, the first one-seventy-fifth objective ever produced, preceding the exhibition by a lecture, in which he gave the history, construction, and uses of this most remarkable lens—the same one, by the way, mentioned by Joseph Cook in one of his Monday lectures. Until within the last ten years, the one-sixteonth-inch objective has been regarded as the highest possible result of optical science, and it was only a few years ago that a distinguished microscopist in this country had to defend the one-sixteenth against the partisans of the old-tashioned quarter and fifth, with the narrow angular aperture. The first man who ever obtained an angular aperture of 180 degrees was Spencer, of this city, who probably succeeded in obtaining that result, but was unable to demonstrate it, although it was conceded by competent judges that his register of 178 was not too high. Most experts will recall an article in the “ American Journal of Science and Art,” published in New Haven, in which this result was set. forth as a remarkable one. Spencer had produced a tenth at this early date, and it was supposed by many that with this, and an angular aperture of 178, the capacity of the microscope was exhausted. Eobert A. Tolies, to whoso ingenuity the lens under descriptf n is due, was graduated as a a pupil with Spencer, and migrated to Boston some years ago. One of his first important lenses was that manufactured for Professor Clarke, of Harvard College, the author of “ Mind in Nature,” and devout follower of Agassiz. This was the famous one-thirty-second, registering a power of 3500 diameters, or 12.250.000 times, with which Professor Wyman and Professor Clarke conducted their once classical inquiries concerning the question of spontaneous generation. In his “ Mind in Nature,” although credit has never been given for the discovery, Professor Clarke was the first to point out and figure the great diversity cf structure which exists among the vibrios and bacteria appearing in infusions. The next remarkable advance in lenses was a fiftieth manufactured by Tolies for Dr. A. G. Hnrriman, of Boston, the discoverer of the nerve fibres in the soft solid matter of the dentine of the teeth, and of the fibrous or tubular structure of dentine. His papers on these discoveries are familiar to students of dental literature. The one-fiftieth did not, however, prove equal to all the emergencies arising in U;e progress of dental histrology, and two years later Dr. Harriman commissioned Tolies to make the seventy-fifth, laying no limitation upon him respecting expenses. The real cost of this powerful objective, which has a working distance of only one two-hundred-and-fiftieth of an inch —that is to say, is that distance from the object when properly adjusted—has been 400dol. That of the one-fiftieth was 250d01. The former (both were on exhibition last night) has an angular aperture of from 173 to 178 degrees, and is composed of three systems of lenses, the posterior being adjustable to cover. At first Dr. Harriman could not find any films of glass thin enough to cover objects and admit of adjusting the objective, and had to overcome the difficulty by using laminae of mica instead of glass. This defect has been obviated, however, and he is now using glass covers of the almost incredible thinness of one-two-hundred-and fiftieth of an inch. The lens is available for photographing, and has, when properly illuminated, a moderately clear definition, but will not bear eye-piercing higher than B. Perhaps an idea of the almost incredible power of such a lens may be obtained from an illustration. The colored corpuscles in human blood were used for the exhibition. These bodies are so minute that it would require about 2,500,000 to pave the surface of a circle half an inch in diameter. The apparent size of such a body under this lens is about that of a ten-cent piece, and the power of the lens, without amplifier, not far from 7500 or 56.250.000 times. Dr, Cutter exhibited the microsphytic growths in the white blood corpuscle in consumption and other minute objects with success.