308 SUMMARY OF CURRENT RESEARCHES RELATING TO 



solution of chloride of calcium, or glycerin, was intended for comparatively 

 low temperatures, being furnished with a special form of thermometer 

 graduated to 150^ C, and as it was somewhat expensive and liable to get 

 out of order, he devised a second form * (fig. 67) which " can be obtained 



for a nominal sum, is capable of being used with an ordinary thermometer, 

 and is available for all temperatures within the range of that instrument." 



A block of copper 6 cm. by 4 cm. by 2 cm., has an aperture 2*5 cm. 

 in diameter passing quite through it, but closed on both sides by thin glass 

 or mica held between thin pieces of cork by means of plates screwed down, 

 as shown in the fig., sufficiently tightly to prevent leakage. A slightly 

 tapering canal is drilled through the block lengthways from one end, 

 meeting and extending a little beyond the aperture. This is for a ther- 

 mometer 33 cm. long, the bulb of which passes across the aperture. The 

 tube is graduated to 600^ F.f An open tube of one piece with the rest 

 communicates with the canal. A piece of copper 3 mm. thick brazed on the 

 block before the aperture is drilled, extends about 15 cm. beyond the end 

 opposite to the thermometer. The part placed on the stage is mounted on 

 some nonconducting substance, such as a piece of well-seasoned mahogany. 



The thin glasses or mica having been firmly packed in their places, and 

 the thermometer put in position, taking care that it does not come into 

 contact with any portion of the metal, perfumed oil is carefully poured into 

 the open tube, until when in a horizontal position it completely fills the 

 aperture in the block ; the whole arrangement is then placed on the stage 

 so that the aperture shall correspond with the optic axis. The object to be 

 examined is placed on the upper thin glass. 



4. Water. — This furnishes by far the best means of heating objects, 

 a constant temperature being more readily maintained than with any other 

 method. Changes of temperature can also be rapidly eff'ected. 



Dr. Polaillon \ suggested a flat box 1 • 0-1 • 5 cm. deep and of the same 

 form as the stage. The upper and lower faces were of glass. There 

 were two indiarubber tubes, one leading from a vessel of hot or cold 

 water placed on a higher level, and the other leading into a lower vessel 

 to catch the waste water. 



Prof. Strieker's § original idea is shown in fig. 68, when the two tubes 

 and rod at the upper side are removed. It consists of a metal box with 

 a central perforation for ligbt, the preparation being either placed upon 

 a cover-glass cemented down, or so arranged that the central aperture 

 serves as a cell. At opposite points of the box two tubes are inserted for 

 the passage of water. 



* Pharmaceutical Journal, xiii. (1882) pp. 1-4 (3 figs.), 21-2. 



t The thermometer was described ns fitted by nieuns of a cork, but Mr. Symons 

 found this got dry and leaked, and subsequently tried cement (sulphur and iron). 

 J Journ. de I'Anat. et Physiol., 1866, p. 133. 

 § Op. cit., p. xix. 



