INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 707 



inventions ; and in this instance the compound body had been made to 

 slip over the outside of the socket in which the objective had been 

 placed. This plan answered fairly well, but he thought it would be 

 better to have it made to fit rather more easily, and to be secured by 

 a bayonet joint, because, supposing that the power employed was not 

 Eufficieut for the purpose, then inconvenience arose unless the body 

 could be got off again with sufficient ease to ensure the object remain- 

 ing undisturbed by any jerk or movement. With the improvement of 

 the bayonet joint it would be easy to remove the body, and having 

 taken out the first lens, and di'opped in say a ^-inch, the body would go 

 on again without any disturbance. He had the instrument before them 

 made upon that pattern, to see how the thing would work ; he had used 

 it for the past six or eight months incessantly, and he could certainly 

 say that for his requirements it was the best thing he had seen, and he 

 believed that with the little addition of a bayonet joint it would be as 

 nearly perfect as any instrument of the kind could well be. He 

 thought that all persons who had been occupied in making minute 

 dissections would see that it had value, and met all the requirements of 

 the most delicate work. He hoped that the members would examine 

 and criticize it, and make any suggestions that occtured to them for 

 its further improvement, for it was becoming of very great importance 

 to examine thin sections and minute portions of dissections without 

 subjecting them to any such disturbance as to cause the slightest 

 alteration, and it was equally important to be able to bring to bear upon 

 them under such conditions the highest powei's that might be needed." 



Nachet's Chemical Microscope.* — In this Microscope (shown in 

 Fig. 57) the objective is placed beneath the object on a brass box 

 containing a mirror silvered on its upper surface. To this box is 

 screwed the body containing the eye-jjiece and a sliding tube which 

 is used as a coarse adjustment. The silvered surface of the mirror 

 is entirely protected from the action of the air, as the two oi)enincrs 

 of the box are furnished with jiarallel glass plates. The focal ad- 

 justment is made by raising the objective and by the micrometric 

 screw V which moves the stage. On the latter is a circular glass 

 cell C, the bottom of which is pierced with a hole of 18 mm., closed 

 by thin cover-glass well luted with Caaada balsam or with silicate 

 of potasli. The object to be examined is placed on the thin glass. 

 An arm B carries a mirror which reflects light from above upon the 

 object in the cell. The latter is provided with two glass taps R R', 

 and is covered by a disk of plane glass hermetically sealed by a little 

 glycerine or grease placed around the edge of the cell. Three small 

 brass uprights keep the coll and its cover in place and immovable. 

 The instrument has a new arrangement for seeing the diflereut parts 

 of the preparation. The body, and consequently tlie objective, is 

 moved by means of two transverse screws O and T. The plate which 

 supports the box is furnished with two transverse divisions in con- 

 nection with the movement of the screws, so as to have in eflect a 

 finder (the divisions aro not represented in the figure). 



* Tmnslated (with 8lip;lit nltorntinns) from note furnislied by M. Naohet. 



3 A 2 



