RICHARDS. THE ELIMINATION OF THERMOMETRY LAG. 



17 



As before, the lag of the thermometer was found, both for the initial 

 and the fiual readings, by drawing a tangent to the curve C at the angle 

 determined respectively by v and t/, the rates of cooling. The results 

 of this graphic computation are recorded in the table below. 



Correction of above Results for Tiiermometric Lag. 



Thus the true average result is lower than that given by the Reg- 

 nault-Pfaundler formula by 0.0064°, or by 0.22 per cent. 



A satisfactory value having been thus found by one method, it be- 

 came a matter of great interest to execute the second series by the 

 method of warming the environment, in order to determine whether or 

 not this would yield the same result. For this purpose the dilute acid 

 placed in the outer jacket of the calorimeter was strongly agitated by a 

 jiowerful stirrer, and at the moment of the experiment a beakerful of 

 alkali of suitable amount was very rapidly poured into it. The tem- 

 peratures inside and out were so arranged that the final temperatures 

 were read on almost if not quite stationary thermometers, the lag of 

 which was negligible. To accomplish this the final outside temperature 

 had to be slightly above the final inside temperature, because of the par- 

 tially unprotected top of the calorimeter. The initial and final tempera- 

 tures were about the same as before, and every other condition of the 

 experiment remained unchanged. The expression of the data is far 

 simpler than before, it being necessary to give only the initial and final 

 temperatures and the correction for the temperature deviation of the 

 alkali delivered into the inner vessel ; and even the latter might have 

 been omitted if somewhat more time had been allowed it in order that it 

 vol. xli. — 2 



