ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 1019 



55, Wigmore Street, W. It was exhibited at the meeting of the Medical 

 Congress at Dublin in August, where it was reported * to have " proved 

 itself infinitely superior to the oxyhydrogen limelight as a means of class 

 demonstration." 



At the Hygienic Congress in Vienna, Prof. S. Strieker also gave demon- 

 strations with the electric Microscope, which, it is claimed,f conclusively 

 prove the value of this new method of medical teaching. Among other 

 things, Prof. Strieker exhibited photographs by transmitted light, with 

 1400 linear amplification, and a section through the spinal marrow of an 

 adult man, in which the ramifications and crossings of the nerves could be 

 most clearly seen. A demonstration was also made with incident light and 

 an amplification of 72,000 times, the object being the exposed pulsating 

 heart of a turtle. " The whole action of the heart could be followed in the 

 most surprising manner, the flow of blood to the great aorta could be 

 observed, and an insight obtained into the inner life to an extent which is 

 seldom realized by experienced students of bygiene." 



Leach's Lantern Microscope. t — At the Soiree of the Manchester Micro- 

 scopical Society, on the 29th January, 1887, Mr. W. Leach exhibited a 

 Lantern Microscope, attached to a photographic camera, the bellows body 

 of which opened out to thirty-six inches. With a 4/10 in. objective, images 

 were shown upon the screen magnified eighty diameters, and " were seen 

 well defined, brilliantly and equally lighted, without covering being placed 

 over the camera, notwithstanding the gaslights overhead and all around the 

 room. The field was noted for being as even as a sheet of writing-paper. 

 When the lantern door was opened much astonishment was expressed, when 

 it was seen that all this illumination was obtained from a small paraffin 

 lamp burning with a single half-inch wick." 



The author in his paper describes his experiments and results as 

 follows : — 



" It is some eight or ten years since I felt dissatisfied with the results 

 which I was then able to obtain with the ordinary lantern arrangements for 

 projecting microscopic objects upon the screen, and began to make experi- 

 ments with the aim of getting more successful illumination. The amount 

 of light transmitted through the bi-lens lantern condenser being in the 

 inverse ratio of the square of the distance between it and the luminant, I 

 tried to shorten the space by the well-known device, first introduced by the 

 Eev. W, T. Kingsley about 1855, of adding a third lens to the other two, 

 and thus shortening the compound focus. But this I soon found was, 

 without further addition, of no use whatever, as the cone of rays at its apex 

 was so large, or the light passed through it at so great an angle, that it 

 was impossible to transmit it through both the object and the objective. 

 Thus the beam of light, however strong it might be at the focus of the 

 condenser, did not reach the screen, and therefore served no purpose except 

 that of boiling the object in the balsam used in mounting it. 



I next placed another lens in the cone of rays a little beyond the focus, 

 and hoped by this means to so lessen its diameter as to make it capable of 

 transmission. This was a sort of substage arrangement, and was found to 

 be a great improvement when the lens was of the right focus for the 

 objective, and was situated at the right distance from both it and the object. 

 To be able to thus place it at the right distance from both, meant having a 

 substage lens for all objectives differing widely in power, the focus of each 

 being such as tlie power and construction of the others might require. 



* Brit. Med. Journ.. 1887, Aug. 27, p. 470. 



+ Central-Ztg. f. Opt. u. Mech., viii. (1887) p. 250. 



t Brit. Jouru. of Phut., xxxiv. (1887) pp. 153-4. 



