84 



with the human body ,- and that the same principle is taken advantage 

 of in producing local Anaesthesia by the use of Rhigoline in freezing 

 the portion of the body to be operated upon. Mr. Bicknell farther 

 cited the sudden fall of the mercury in the wet-bulb thermometer, on 

 wetting the bulb to determine the dew-point, which effect is produced 

 by the evaporation of the moisture from the bulb. 



The Kev. E. 8. Atwood made a few remarks on the uses in the 

 East of earthen jars with a small mouth, for the purpose of keeping 

 water cool, and of the formation of ice on the outside of the jars con- 

 sequent upon the evaporation of the water. 



Mr. Hyatt made some remarks confirming Mr. Bicknell's theory, 

 and alluded to the temperature in deep mines and caverns. All the 

 cases of ice formations occur only in shallow wells, such as the Bran- 

 don well, or in caverns of limited extent, such as the one described, 

 where the water is subject to rapid evaporation during the summer 

 months. In deep mines and caverns, the temperature remains con- 

 stant all the year round. The temperature of the earth increases 

 about one degree for every fifty or sixty feet of descent. In winter, 

 the air of the mine or cavern is warmer than the air on the surface ; 

 thus there is a continual rush of the interior heated air toward the 

 .surface, and a corresponding inflowing of the cooler air from above. 

 During the summer this process is often reversed, the air in some 

 caverns, which are not very deep, being at a lower temperature, 

 rushes outward, and is replaced by an influx of the more heated at- 

 mosphere from the surface. This circulation maintains an equable 

 decree of heat, prevents evaporation, and keeps ice from forming to 

 any appreciable extent either in winter or summer. 



But this circulation does not take place in shallow caverns or wells 

 to any great extent, and the water is evaporated rapidly by the heat 

 of the sun in summer, causing the congelation described by Mr. Bick- 

 uell. Mr. Hyatt also said that the freezing of water upon the earthen 

 jars during the hottest weather in the East, as mentioned by Kev. Mr. 

 Atwood, could be accounted for in the same way. The evaporating 

 water taking away so much heat from the water, as it exuded through 

 the jar, that a portion of it would freeze. 



Mr. Bickuell exhibited a 4-10th inch' object-glass, made by K. B. 

 Tolles, of Canastota, New York. This objective had attached to it an 

 " Opaque Illuminator," consisting of a prism of glass inserted in the 

 mounting of the objective, between the front lens and the rest of the 

 combination. Light being thrown into the prism is reflected down 

 through the front lens (which thus becomes the condenser), and is 

 thrown upon the object to be viewed, giving it a very beautiful and 

 brilliant illumination, with ample light for all purposes, and bearing 



