Translation of Key's Essays. 267 



lected, willsbow tlie dilatation of the air in the intestine, to which 

 the capacity of the teohpile being added, the question is solved. 

 To these well-ascertained methods, I add the following, not un- 

 plausible one, for converting air into water, and ascertaining 

 the diminution of volume. Let the hole of the before-men- 

 tioned tube, be closed, and the piston pushed down with great 

 force, as far as the compression of the enclosed air will permit, 

 and stopping it at that point, so that it cannot fly back, expose 

 the apparatus to a frosty air, for a whole night; the air com- 

 pressed on the inside, will freeze, or be converted into water, 

 leaving only that space occupied by the air, which may remain 

 free, {i. e., unfrozen.) The measure of the water, or the ice, will 

 give the loss of volume. I have not made this experiment: 

 if any curious person is beforehand with me, I request he will 

 give me an account of the result, as all the reward I ask for 

 having taught him the method, and to the end that I may be 

 spared the trouble. 



A the ceolipile ; B its tube, entering the brass tube ; C the 

 brass tube ; D its piston ; E the piston rod. 



ESS.4Y VIII. 



No element gravitates in itself, and why? 

 I resume my argument, and say, that the examination of 

 weights by the balance differs greatly from that by reason. 

 The latter is only employed by the man of judgment, the rudest 

 clown practises the former. This is always just, that is gene- 

 rally^ deceitful ; this is attached to no circumstance of place; 

 that commonly exercised in air, and sometimes, though diffi- 

 cultly, in water. It is hence, that the error which I have com- 

 bated, (that air has no weight,) derives an argument capable 

 of dazzling weak eyes, but not the clear-sighted. For weighing 

 air in itself, and not finding it to gravitate, they have concluded 

 that it has no weight. But let them weigh water, (which they 

 believe to have weight,) in water itself, and they will find it 

 otiually void of it, it being most true, that no element gravitates 

 in itself. Whatever gravitates in air, whatever gravitates in 

 water, must contain more weight in an equal volume (in conse- 

 (jucncc of there being more matter) than the Jiir or water, in 



