THE SUCCESSORS OF GALILEO 



what larger," he says, "when it seemed to be dead, the 

 air was readmitted, and soon after it revived; putting 

 it again in the vacuum, and leaving it for an hour, after 

 which the air was readmitted, it was observed that the 

 insect required a longer time to recover; including it 

 the third time for two days, after which the air was 

 admitted, it was ten hours before it began to stir ; but, 

 putting it in a fourth time, for eight days, it never 

 afterwards recovered. . . . Several birds, rats, mice, 

 rabbits, and cats were killed in a vacuum, but if the air 

 was admitted before the engine was quite exhausted 

 some of them would recover; yet none revived that 

 had been in a perfect vacuum. . . . Upon putting 

 the weight of eighteen grains of powder with a gauge 

 into a receiver that held several pounds of water, and 

 firing the powder, it raised the mercury an inch and 

 a half ; from which it appears that there is one-fifth of 

 air in gunpowder, upon the supposition that air is 

 about one thousand times lighter than water; for in 

 this experiment the mercury rose to the eighteenth 

 part of the height at which the air commonly sustains 

 it, and consequently the weight of eighteen grains of 

 powder yielded air enough to fill the eighteenth part 

 of a receiver that contained seven pounds of water; 

 now this eighteenth part contains forty-nine drachms 

 of water; wherefore the air, that takes up an equal 

 space, being a thousand times lighter, weighs one- 

 thousandth part of forty-nine drachms, which is more 

 than three grains and a half ; it follows, therefore, that 

 the weight of eighteen grains of powder contains more 

 than three and a half of air, which is about one-fifth 

 of eighteen grains. ..." 



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