22 



A DISCOURSE 



BOOK I. three feet higli ; lay the first foot in fine earth, another of Seeds, Acorns, 

 "^'^'^^^ Mast, Keys, Nuts, Haws, Holly-berries, &c. promiscuously or separate, 

 with, now and then, a little mould sprinkled amongst them ; the third 

 foot wholly earth : Of these preparatory magazines make as many and as 

 much larger ones as will serve your turn, continuing it from time to time 

 as your store is brought in. The same you may also do for ruder hand- 



" The air, on which I made the first experiments, was rendered exceedingly noxious by 

 " mice dying in it on the 20th of June. Into a jar nearly filled with one part of this air, 

 " I put a sprig of mint, while I kept another part of it in a phial, in the same exposure ; 

 " and on the 27th of the same month (and not before) I made a trial of them, by intro- 

 " ducing a mouse into a glass vessel, containing 2^ ounce measures filled with each kind 

 " of air ; and I noted the following facts. When the vessel was filled with the air in 

 "which the mint had grown, a very large mouse lived five minutes in it, before it began to 

 " show any sign of uneasiness. I then took it out, and found it to be as strong and 

 " vigorous as when it was first put in ; whereas in that air which had been kept in the 

 " phial only, without a plant growing it, a younger mouse continued not longer than 

 " two or three seconds, and was taken out quite dead. It never breathed after, and was 

 " immediately motionless. After half an hour, in which time the larger mouse (which I 

 " had kept alive, that the experiment might be made on both the kinds of air with the 

 " very same animal) would have been sufficiently recruited, supposing it to have received 

 " any injury by the former experiment, it was put into the same vessel of air ; but though it 

 " was withdi'awn again, after being in it hardly one second, it was recovered with 

 " difficulty, not being able to stir from the place for near a minute. After two days, I 

 " put the same mouse into an equal quantity of common air, and observed that it continued 

 " seven minutes without any sign of uneasiness ; and being very uneasy after three 

 " minutes longer, I took it out. Upon the whole, I concluded that the restored air wanted 

 about one-fourth of being as wholesome as common air. The same thing also appeared 

 " when I applied the test of nitrous air. In the seven days, in which the mint was 

 " growing in this jar of noxious air, three old shoots had extended themselves about three 

 " inches, and several new ones had made their appearance in the same time. Dr. Franklin 

 " and Sir John Pringle happened to be with me, when the plant had been three or four 

 "days in this state, and took notice of its vigorous vegetation, and remarkably healthy 

 " appearance in that confinement. On the SOth of the same month, a mouse lived 

 " fourteen minutes, breathing naturally all the time, and without appearing to be much 

 " uneasy, till the last two minutes, in the vessel containing two ounce measures and a 

 " half of air, which had been rendered noxious by mice breathing in it almost a year 

 " before, and which I had found to be most highly noxious on the IQth of this month, a 

 " plant having grown in it, but not exceedingly well, these eleven days ; on which 

 " account I had deferred making the trial so long. The restored air was effected by a 

 " mixture of nitrous air, almost as much as common air. As this putrid air was thus easily 

 " restored to a considerable degree of fitness for respiration, by plants growing in it, I 



