158 THE AMERICAN MONTHLY [.July, 



A remarkable collection of batteries, dynamos, and lights suit- 

 able for microscopical use was exhibited by the great French 

 electrician, G. Trouve. of Paris. His " photophore," consisting 

 of a little drum containing a bull's-eye lens with a tiny electric 

 loop behind it, the whole sliding easil}' up or down a vertical 

 pillar and capable of turning at any angle, like the search-light of 

 a ship, seems by far the best electrical illuminator yet produced. 

 It apparently needs only to be freed from its dependence on the 

 necessarily troublesome battery by the presence of an electric 

 service-wire in every house to become the illuminator of the mi- 

 croscope. By this exhibit. AI. Trouve, whose biography, lately 

 published in a fascinating book as '' The History of an Inventor," 

 seems more like a romance than a history, added another diploma 

 of honor to a former list of awards of which any inventor in any 

 line of research might well be proud. 



Photomicrography. 



This class was, of course, exceptionally prominent. The appa- 

 ratus pertaining to it was mostly included in the makers' exhibits 

 of microscopes and accessories. 



A. Nachet, of Paris, whose personal experience in photomicrog- 

 raphy insures a special interest in the work and an exceptional 

 familiarity with its demands, was first in the variety of his appli- 

 ances and unsurpassed in their quality and completeness. His 

 "•grand apparatus" has a horizontal bellows capable of easy ad- 

 justment for distances up to about two meters. The stand is 

 placed horizontall}' in connection with this ; but it has also an 

 extra body branching vertically from the main body, just behind 

 the objective, and supplied with a sliding prism which serves, 

 when racked down, to totally reflect the light from the objective 

 up through the vertical tube which is used for observation while 

 adjusting the object and the illumination, and when racked up 

 permits the same pencils to pass horizontally directly to the sen- 

 sitive plate at the far end of the bellows. His " petite apparatus " 

 designed for elementary work is very simple, the dark chamber 

 being a plain box supported over the ocular end of an ordinary 

 microscope standing either vertically or inclined. This box, with 

 its sensitive plate at the top, can be clamped at various heights 

 upon a pair of parallel supporting bars, the latter being jointed at 

 the level of the microscope stage, so that they may be maintained 

 parallel with the body at any desired inclination. His mammoth 

 style of " inverted microscope" (which will be remembered as a 

 conspicuous feature of his exhibit at our Centennial exhibition at 

 Philadelphia in 1S76) is also fitted with an inverted dark chamber 

 which is supported upon the top of the inclined tube, and which, 

 with such a support, has naturally the advantage of extreme stead- 

 iness. But Nachet's most unique device is the apparatus for in- 

 stantaneous photography of living objects, as infusoria, etc. This 

 is an elaborate and finelv-bu.lt aflhir. The inverted dark cham 



