22 Prof. A. Battelli and Mr. L. Magri on 



the displacement of the liquid column in a capillary tube. 

 If the tube be not of perfectly constant calibre, this displace- 

 ment is influenced to a notable degree by the capillary 

 action. 



7. Standardizing of Calorimeters. 



22. In order to obtain in absolute measure from the dis- 

 placement of the meniscus in the capillary tube of the calori- 

 meters the energy evolved within them we effected their 

 standardizing in the following maimer : — 



(a) In the case of the metallic spiral calorimeters there 

 was kept on during a given time a continuous current of 

 known intensity, from whose value, together with the value 

 of the resistance offered by the spiral to continuous currents 

 (this resistance being measured by an Elliott bridge), the 

 energy spent in the spiral was calculated, and hence the 

 relation between this energy and the displacement of the toluol 

 column in the calorimeter was obtained. 



(b) In the case of the spark calorimeter we proceeded in 

 the same manner, after, however, connecting the two ter- 

 minals of the spark-gap with a small constantan spiral of 

 known resistance. 



The readings of the calorimeters — made at a distance with 

 a telescope — were effected in both cases by determining from 

 minute to minute the displacements presented by the top of 

 the toluol column five minutes before beginning experiments, 

 during experiments, and five minutes afterwards. 



The passage of the continuous current during the standar- 

 dizing experiments, as well as the passage of discharges 

 during those of definitive measurements, did not last beyond 

 40 seconds. Readings were always taken by night, in order 

 to have as small variations as possible of temperature in the 

 room, and heat changes with the exterior were taken account 

 of by calculations analogous to those made in pyrheliometric 

 researches. 



In the table below the data relative to the five calorimeters 

 we made use of during our researches are recorded. 





Spiral Calorimeter. 











Extern. 









Diam. of 



Diameter of 



No. of 



Length 





wire, cm. 



spiral, cm. 



turns. 



of spiral. 



Oalor. No. 1.. 



. 0-078 



1-521 



220-25 



36"K 



„ „ 2.. 



. 0-078 



1-78 



423 



69 





. 0-078 



1-61 



102 



15-6 



