232 now TO WORK 



::::::. History of the Aii>Hcatioa of I'liotnsriipliy to tlie Microscope.* 



Mr. Dancer, about 1840, produced photographs of microscopic 

 objects by the .{.w microscope, the images being taken upon silvered 

 plates; also images of sections of wood, fossils, <S:c., were reproduced 

 on paper and glass plates by means of the solar microscope. In 

 1841, Mr. Richard Hodgson obtained excellent daguerreotypes of 

 microscopic objects. The Rev. Messrs. Reade and Kingsley were early 

 authorities in the employment of photography in this manner; also 

 Mr. Talbot. Dr. Donne, of Paris, in 1840, presented to the Academy 

 of Sciences copies of various microscopic objects on daguerreotype 

 plates; and in 1845, conjointly with M. Leon Foucault, published 

 an Atlas of Microscopic Anatomy, in which the engravings were 

 printed from daguerreotype plates, which after exposure and deve- 

 lopment had been chemically etched. The delicacy of these illustra- 

 tions was very marked, but the plates permitted comparatively few 

 impressions to be struck off before giving evidence of injury. 



In October, 1852, a paper by Mr. Joseph Delves was presented 

 to the Microscopical Society of London, and in the following number 

 of the " Quarterly Journal of Microscopical Science," some beautiful 

 specimens of prints from Mr. Delves' collodion negatives were issued 

 by the then publisher, Mr. Highley. This was one of the earliest 

 publications in this country with photographic illustrations of micro- 

 scopic specimens. In the same journal is a valuable contribution 

 by Mr. G. Shadbolt. Since that period the employment of photo- 

 graphy in this way has become general ; doubtless many have been 

 occupied with it whose names are not familiar to us. In Paris 

 M. Nachet and M. Bertsch have obtained excellent results. In 

 Germany, Gerlach, Albert, Mayer, Kolmann of Munich, Helwig of 

 Mayence, and many others have illustrated memoirs with photo- 

 graphic plates. Sir D. Brewster, in his article Microscope, " Ency- 

 clopaedia Britannica," last edition, speaks veiy highly of some 

 photomicrographs exhibited at the Academy of Sciences, Paris, in 

 l $S7> by M. Bertsch, the focal length of the objective used being 

 half a millimetre. The objects, a diatom from guano magnified 

 500 diam. ; two specimens of navicula, one x 800, the other X 500, 

 the field being rendered nearly dark by oblique illumination ; human 

 blood globules x 500 ; and two pictures of salicine, one taken by 

 polarised light. M. Hartnach, Sir D. Brewster says, has constructed 

 a complete instrument for M. Bertsch, the range being from 50 to 

 1,000 diameters, and from 50 to 150 diameters for opaque objects. 



' The sections in this part of the work have been carefully revised by Dr. 

 Maddox, who has kindly added much new matter of great importance, especially 

 in 3 2 7> 33 2 > 33 8 . "wy. 



