OF ARTS AN.T) SCIENCES. 199 



tne air thermometers, I ignored small irregularities and drew a regu- 

 lar curve. On looking over the observations again, I see that, had I 

 taken account of the small irregularities, it would have made the ob- 

 servations agree more nearly with the other thermometers. Hence 

 the objection vanishes. However, I intend working up some obser- 

 vations which I have with the Kew standard at a higher temperature, 

 and shall publish them at a future time. 



There is one other error that might produce an apparent decrease 

 in the specific heat, and that is the slight decrease in the torsion weight 

 from the beginning to the end of most of the experiments, probably due 

 to the slowing of the engine. By this means the torsion circle might 

 lag behind. I made quite an investigation to see if this source of error 

 existed, and came to the conclusion that it produced no perceptible 

 effect. An examination of the different experiments shows this also ; 

 for in some of them the weight increases instead of decreases. See 

 Tables XXXVII. to L. 



The error from the formation of dew might also cause an apparent 

 decrease ; but I have convinced myself by experiment, and others can 

 convince themselves from the tables, that this error is also inappre- 

 ciable. 



The observations seem to settle the point with regard to the specific 

 heat at the 4° point within reasonable limits. There does not seem 

 to be a change to any great extent at that point, but the specific 

 heat decreases continuously through that point. It would hardly be 

 possible to arrive at this so accurately as I have done by any method 

 of mixture, for Pfaundler and Platter, who examined this point, could 

 not obtain results within one per cent, while mine show the fact 

 within a fraction of one per cent. 



The point of minimum cannot be said to be known, though I have 

 placed it provisionally between 30° and 35° C, but it may vary much 

 from that. 



The method of obtaining the specific heat of the calorimeter seems 

 to be good. The use of solder introduces an uncertainty, but it is too 

 small to affect the result appreciably. The different determinations 

 of the specific heat of the calorimeter do not agree so well' as they 

 might; but the error in the equivalent resulting from this error is very 

 6mall, and, besides, the mean result agrees well with the calculated 

 result. It may be regarded as satisfactory. 



The apparatus for determining the equivalent could scarcely be 

 improved much, although perhaps the record of the torsion might be 

 made automatic and continuous. The experiment, however, might be 



