[ »76 ] 



'I once imagined that, fince fixed and inflammable 

 air are the reverfe of one another, in feveral remark- 

 able properties, a mixture of them would make 

 common air; and while I made the mixtures in 

 bladders, I imagined that I had iiicceeded in my 

 attempt ; but I have fince found that thin bladders 

 do not fufhciently prevent the air that is contained in 

 them from mixing with the external air. Alfo corks 

 will not fufficiently confine different kinds of air, 

 unlefs the phials in which they are confined be fet 

 with their mouths downwards, and a little water lie 

 in the necks of them, which, indeed, is equivalent 

 to the air ftanding in veffels immerfed in water. In 

 this manner, however, I have kept different kinds of 

 air for feveral years. 



Whatever methods I took to promote the mixture 

 of fixed and inflammable air, they were all ineffec- 

 tual. I think it my duty, however, to recite the 

 iffue of an experiment or two of this kind, in which 

 equal mixtures of thefe two kinds of air had flood 

 near three years, as they feem to ihew that they had 

 in part affected one another, in that long fpace of 

 time. Thefe mixtures I examined April 27, 1771. 

 One of them had flood in quickfilver, and the other 

 in a corked phial, with a little water in it. On 

 opening the latter in water, the water inflantly rufhed 

 in, and filled almofl half of the phial, and very little 

 more was abforbed afterwards. In this cafe the water 

 in the phial had probably abforbed a confiderable part 

 of the fixed air, fo that the inflammable air was 

 exceedingly rarefied -, and yet the whole quantity 

 that muff have been rendered non-elaftic was ten 

 times more than the bulk of the water, and it has 



not 



