142 Intelligence and Miscellaneous Articles. 



apparently replaced by the freshwater deposits of the German 

 Wealden. 



2. " On Deep -mining with relation to the Physical Structure and 

 Mineral-bearing Strata of the S.W. of Ireland." By Samuel Hyde, 

 Esq. Communicated by R. Etheridge, Esq., F.G.S. 



XVI II. Intelligence and Miscellaneous Articles. 



ON THE USE OF THE EXECTRIC CURRENT IN CALORTMETRY. 

 BY M. J. JAMIN. 



JOULE'S law gives the heat which is developed in conductors 

 when traversed by currents. A metal wire may be regarded as 

 a focus. It may have any possible form and be placed where we 

 please, in the midst of liquids or gases ; a quantity of heat will be 

 given off proportional to the time, to its resistance, and to the square 

 of the intensity of the current ; it will heat those bodies by a quan- 

 tity which can be measured, and which is inversely proportional to 

 their mass and to their specific heat. Hence results a new process 

 to determine this specific heat. After numerons trials 1 fixed upon 

 the following arrangements. 



I. Case of Solids and of Liquids . — In dealing with a solid or a liquid, 

 I use as a calorimeter an elongated cylindrical vessel of thin copper, 

 on which is coiled 8 metres of German-silver wire 0"2 millim. in dia- 

 meter, and covered with silk. This spiral commences at the bottom 

 of the vessel, and ascends to one-third of its height ; it is connected 

 with the circuit by thick copper wires ; its resistance is measured 

 for all the temperatures of the experiment. I envelope it with a thin 

 silk ribbon to keep it in its place, some swan's down to insulate it, and 

 I enclose the whole in an envelope of thin copper polished. When 

 the calorimeter contains a liquid and a current is caused to pass 

 through the spiral, nearly all the heat will be transmitted to the sides, 

 then to the liquid ; a scarcely appreciable portion will be transmitted 

 to the swan's down. 



With this view, fresh liquid must be continually brought into con- 

 tact with the sides by uniform agitation. For this purpose a basket 

 of metal gauze, formed of two concentric tubes, is immersed in the 

 calorimeter. A small machine raises and lowers it at equal intervals ; 

 a thermometer marking the hundredth of a degree is immersed in 

 the central tube ; it is fixed, and is read with a telescope. When the 

 specific heat of solids is to be measured, they are placed in the basket 

 in the water. 



This constitutes the entire apparatus ; the operation is one of ex- 

 treme simplicity. After pouring into the calorimeter the weight of 

 liquid which is to be investigated and agitating it some time, the 

 variation (if any) of the thermometer is observed for five minutes. 

 Generally it does not vary. A current of a measured intensity is 

 then made to pass during one, two, &c. minutes, until an elevation 



