Chemistry and Physics. 455 
attention, and to give no more explanatory matter than is actually 
required to render each subject perfectly intelligible.” It is 
Sip in the apparatus for producing these curves. Two 
tge tuning forks are maintained in vibration by an electric cur- 
rent circulating around a magnet placed between the prongs. Tk e 
itch is regulated approximately by two weights of five or six 
" : 
ll. Mechanical Equivalent of Heat.—The committee of the 
British Association appointed to determine this constant, report 
progress as follows: Dr. Joule has been engaged in further meas- 
ements by means of the friction of water, and as the average 
Tesult of sixty experiments gives 772°2 in British gra 
at Manchester, The greatest deviation from the above average 
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this source is pr Y $y and that from the incorrect boiling 
Point of the thermometers ximum value of these two 
_12. Ohm’s Law.—Prof. Maxw#1t presented to the [ 
lation at their last meeting the Report of the -oageg ome fed 
Testing Experimentally the Exactness of Ohm’s Law. The p 
