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II. — ON A NEW FORM OF CALOEIMETEK. By W. F. 

 BARRETT, Professor of Physics in the Royal College of 

 Science, Dublin. 



[Read, June 15, 1885.] 



An accurate mode of determining the specific heat of bodies, with- 

 out the serious corrections that have to be introduced in the ordi- 

 nary method of mixtures, is much needed. Mr. Joly has lately 

 devised and described before the Boyal Dublin Society a novel 

 and ingenious method depending on the amount of steam con- 

 densed by the body ; but I have not found this method answer so 

 well for determining specific heats as for latent heats of vaporiza- 

 tion ; in the latter case it leaves little to be desired. 1 



The method devised by Professor Bunsen is well known. A con- 

 venient modification of Bunsen's calorimeter was made some time 

 ago by Professor Emerson Reynolds, wherein the calorimeter takes 

 the form of an alcohol thermometer with a large bulb, and having an 

 arbitrary scale, the value of which is determined separately. The 

 instrument I now beg to submit to the Society resembles the fore- 

 going in so far as the cup for holding the body under experiment 

 forms a portion of the thermometer, which, however is mercurial, 

 and has a very open scale. The instrument is shown in the wood- 

 cut on next page, and its present form is mainly due to the valu- 

 able suggestions made, in the course of working with it, by Mr. 

 J. M'Cowan, the Demonstrator of Physics in this College. As a 

 piece of glass-blowing it is, I believe, unrivalled, and is a testimony 

 to the skill of Mr. Hicks of Hatton Garden, London, who under- 

 took to make it for me, and who informs me that the cup is blown 

 out of a single piece of glass tubing. 2 



The cup, A, has a capacity of about 4 cubic centimetres ; it is 

 surrounded by a jacket of polished metal, 3 to prevent any slight loss 



1 I understand Mr. Joly has since improved his apparatus for rinding specific 

 heats. 



2 Since this Paper was read, Mr. Hicks has made several of these instruments, and 

 can now produce them at a moderate cost. 



3 A simpler expedient is to silver the outside of the bulb of the thermometer by 

 Liebig's process. 



