﻿168 Prof. R. Bunsen's Calorimetric Researches. 



fibrous texture entirely disappears. The ice between \ and fi 

 now consists of smooth rounded transparent grains. If the in- 

 strument, after continued use, is exposed to the heat of the 

 room, the single grains melt on their surface, and thereby free 

 themselves from each other and ascend in the liquid, and in doing 

 so occasionally appear like globules of the yeast plant strung 

 together. In order, then, to understand more clearly the for- 

 mation of ice, so far as the use of the instrument is concerned, 

 the calorimeter, with its ice-cylinder carefully surrounded by 

 snow, was observed for a considerable time. The instrument in 

 this and in all the following experiments was placed in a large 

 earthenware decanting-jar, from the lower aperture in which the 

 water formed by the melting of the snow could constantly flow 

 out; in this way contact of the lower part of the instrument with 

 the water was avoided. The instrument soon becomes surrounded 

 with a compact mass of congealed snow (Firneis) . If after twelve 

 or fifteen hours, owing to external melting of this ice, a consider- 

 able space is formed at the sides of the jar, this space is in- 

 creased by cutting away with a wooden spatula the loosely 

 caked Firneis, which is pushed below the calorimeter and its 

 place supplied by fresh snow. The first experiment was made 

 with fresh-fallen snow which was perfectly free from earthy im- 

 purities. Some hundredweights of this snow were preserved in 

 a clean wooden box as a supply for refilling during the experi- 

 ments. With such a supply the calorimeter can be kept work- 

 ing for a whole week, and refilled twice daily without the ice- 

 cylinder needing to be renewed. During the whole length of 

 the observations, which took five days, the inner vessel, sur- 

 rounded by a cylinder of ice, was closed with an india-rubber 

 stopper, and the whole instrument, with the exception of the 

 scale, enclosed on every side with melting snow. The tempera- 

 ture of the room in which the experiments were made varied 

 from o, 5 C. to 6° C. The experiments are collected in Table I. 

 Column I. contains the times of the observations in hours ; 

 column II. gives the readings of the calorimeter-scale during 

 the same times ; those marked with asterisks are the observed 

 values, from which the remaining ones are calculated by in- 

 terpolation. The mercury which escaped from the scale-tube 

 was weighed up to the thirty-first hour, and the weights found 

 converted into divisions of the scale by means of equation (1) . 

 Column III. is calculated by means of equation (3), and repre- 

 sents the weight in grammes of the ice formed in the instrument 

 from the commencement of the time. 



