20 An Inquiry concerning 



Time when weighed. Was found to weigh. 



Atsh. im ...... 774^ grains. 



3 '8 ..... 774M- " 



* 3 25 . . . 774J 



6 15 ... 



Immediately after this last-mentioned weighing of 

 the bullet, the whole of the apparatus appearing to have 

 acquired the temperature of the air in the room (60 F.), 

 the bullet was taken away, and the porcelain stand and 

 cup were again balanced in the scale, when it appeared 

 that they had lost \ of a grain in weight during the 

 preceding experiment. This apparent loss of weight I 

 could ascribe to nothing but to the thorough drying of 

 the cups in the experiment with the red-hot bullet, and 

 to the drying of the silk cords by which the scale con- 

 taining the cup and stand was suspended to the arm of 

 the balance. 



This weight == \ of a grain, which was required to 

 balance the scales at the end of the experiment, being 

 added to the apparent weight of the bullet at 6 h. 15 m. 

 774i> i ts true weight at that time appears to have 

 been 775^. 



The weight of the bullet at i h. 30 m. having been no 

 more than 773^ grains, and at 6 h. 15 m. it being found 

 to weigh 775^f grains, it appears that it had gained in 

 weight by being heated red-hot 775 Jf 773 /T = 2 i 

 grains. 



This augmentation of weight doubtless arose from 

 the partial oxidation of the iron. It certainly did not 

 arise from the heat, for it remained after the bullet had 

 become cold. 



* Just before this weighing, the coffee-cup which covered the bullet in the scale 

 had been removed for a moment to look at the bullet, and then immediately re- 

 placed. What it was that escaped on this occasion I will not undertake to say, but 

 certain it is that its weight amounted to -fa of a grain, at the least; 



