314 



SUMMARY OF CUBRENT RESEARCHES RELATING TO 



Fig. 78. 



If it is desired to cool the object the end of the vessel i can be placed 

 in cold water, or for low temperatures in ice and salt, the chamber being 

 then filled with pure alcohol instead of water. 



_ The appara,tus can also be used as a moist chamber or for steaming 

 objects. In this case only a little water is placed in i, u being closed with 

 wax and the object placed at g. If the glass h d is too thick one or other 

 of the following plans may be adopted. The object may be placed on b d 

 and covered, and a communication made between the interior (filled with 

 water) by a piece of cotton. Or b d may be removed and a brass plate 

 substituted with a square aperture, over which the object is suspended 

 on a cover- glass. 



For a dry chamber it is only necessary to introduce sulphuric acid 

 or potash sticks into the vessel i. 



Gases can be introduced through s t, the object being suspended over 

 the aperture in the brass plate as before, or the action of the vapour of 

 ether, chloroform, &c., upon different objects may be investigated. 



It is also adapted for all kinds of observations (spectroscopic, fluorescent, 

 or otherwise) on fluids, especially where a constant thickness is required. 



Prof. J. Sachs encloses the Microscope itself in a special chamber 

 which he describes as follows :* — 



" Convenient contrivances for observing the action of particular higher 

 or lower temperatures on plants or parts of plants of considerable size 



are easily arranged. It is more difficult 

 to expose microscopic objects to a par- 

 ticular higher or lower temperature in 

 such a manner that it can easily and cer- 

 tainly be observed, and that the tempera- 

 ture of the object is also that indicated 

 by the thermometer, or nearly so. All 

 these requirements are fulfilled by the 

 very cheap heating apparatus for the 

 Microscope represented in fig. 78. 



The size of the heating apparatus must 

 vary with that of the Microscope ; mine is 

 constructed for one of Hartnack's ordinary 

 instruments. The box is nearly cubical, 

 and has double walls of sheet zinc at the 

 bottom and sides, inclosing a space 25 mm. 

 thick, which is filled with water through 

 the hole I (fig. 78). It is quite open 

 above, but in the front side-wall is an 

 opening /, which is closed by a glass plate 

 well fitted but not otherwise fixed. This 

 window is sufficiently large, and is so 

 placed that it allows enough light to fall 

 on the mirror of the Microscope which 

 stands in the box. The height of the box 

 is so arranged that the upper rim of the 

 double wall is on a level with the arm b of 

 the Microscope. The opening of the box is closed by a thick cardboard 

 cover d d, in which an opening is cut exactly to fit the arm b. By the side of 

 the tube of the Microscope a round hole is cut in the cover through 

 which a closely fitted small thermometer t passes, so that its bulb hangs 



* Sachs, J., * Text-book of EotaDy,' 2nd ed., 1882, i^p. 7^5-7 (1 fig-)- 



