The following description of Gundlach's contributions to microscopical optics was extracted from the Proceedings of the American Society of Microscopists (1882):
ERNST GUNDLACH Was born in Pyritz, Prussia, 1834; was educated there and in Berlin, where he took a course in one of the leading workshops (C.Lewert) to learn the trade of philosophical instrument-maker; afterwards working with other firms, and always choosing those who were doing their own optical work, in the hope of adding practical knowledge to the theoretical principles of optical science with which he was already familiar. On account, however, of the habit of opticians of keeping their methods of work strictly secret, young Gundlach learned little or nothing of practical value in this special line and, in 1866, he started optical work for himself, knowing nothing of the methods of others, except that emery is used for grinding, and rouge for polishing lenses. Technical difficulties soon presented themselves, only to be overcome by the enthusiasm of the young optician, and in about six months he had completed his first microscope, with three objectives and two eye-pieces. This instrument was purchased by Prof. Berg, of the University of Berlin, who, though a stranger to Mr. Gundlach, recognized the fine quality of his work. The next year he exhibited at the Paris Exposition his glycerine immersion objectives, and received therefor a special medal. This Mr. Gundlach believes to be the first instance of the intentional construction of objectives for use with an immersion fluid of higher refractive index than water. A frictionless fine adjustment for microscope stands was another of his inventions about this time.
In 1873 Mr. Gundlach, who had already become recognized as one of the greatest of living opticians, removed to this country and located at Hackensack, N. J. His first work here was the construction of two water immersion objectives (a 1/6 and 1/16 for Prof. Thacker, of Cincinnati, O., which won the admiration of many very competent judges, including Dr. Woodward, of the U. S. A. Medical Museum, Washington, D. C. In 1875, Mr. Gundlach invented his so- called “glycerine adjustment,” in which, by means of a layer of heavy glycerine of variable thickness confined between the front of the anterior lens of the objective and a plane glass cover, compensation is made for varying thickness of cover glass without alteration of optical adjustment or change of magnifying power.
In 1876 Mr. Gundlach brought out his hemispherical condenser and his periscopic eye-piece, the latter being an improvement on the orthoscopic ocular of Kellner.
In 1879 he discovered a new optical principle, upon which the construction of his globe lens is based. The construction of this lens is very peculiar, consisting of a solid and perfect globe of crown glass enclosed in cement within a hollow globe of flint glass, the corrections being obtained by the thickness of the flint.
In 1880 Mr. Gundlach produced a series of homogeneous immersion objectives, having apertures of 136° in balsam (1.41 N. A.), and combining remarkable working distance with most excellent corrections and performance.
Mr. Gundlach has also made some notable contributions to the literature of microscopical optics, among which may be mentioned his discussion of numerical working distance of objectives, and a new method of measuring apertures from 87° to 1800 in crown glass (1.14 to 1.52 N. A.) It will be seen that, so far as practical optics is concerned,'Mr. Gundlach is an autodidact, as, from the secrecy maintained by European opticians in regard to their methods of work, he was unable to learn but little, if anything, and was forced to work out his methods for himself.