ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



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former case the object will be at a lower and in the latter at a bigher 

 temperature than the thermometer. If it is desired to know exactly the 

 temperature of the object a rapid circulation must be maintained, and a 

 thermo-regulator used. 



Dr. G. Valentin's * (fig. 76) is intended not only for heating and 



Fig. 75. 



cooling by water, but also by air, and for a great variety of microscopica 

 observations which require a closed chamber. 



It consists of a vessel i (fig. 76), projecting over the side of the stage, 

 and communicating with the chamber hghj the two pipes j? and m. The 



Fig. 77. 



centre is formed of two glass discs h d and ef, h d being sunk below the 

 level of a c to form an outer chamber, which can be closed with cover- 

 glass when required. It is removable, so as to give access to the interior. 

 (A section of the interior of h g is shown 

 in fig. 77, where ef is the bottom plate of 

 fig. 76 and mp the openings of the two 

 pipes ; a h aud c d are two metal partitions 

 which serve to regulate the flow of the 

 fluid, as shown by the arrows.) A thermo- 

 meter q r also passes into the chamber, 

 which terminates at this end at df. 



To use it for heating with water the 

 top $t is removed and water poured into i 

 until full, and a spirit-lamp placed beneath 

 it. The steam escapes at the small hole at u, or, if the water is required 

 to boil, the top is removed and a pipe of larger opening put on. For 

 heating with air the spirifc-lamp is placed as before, or the vessel i is 

 plunged in hot water. 



* Valentin, G., 'Die physikalische Untersuchung der Gewebe,' 1867, pp. 421-8 

 (4 fi^s.). 



1887. Y 



