VOL. LXX.] PHILOSOPHICAL TRANSACTIONS. dg.T 



of corruption of various substances; and that the liveliness we commonly enjoy 

 in frosty weather is in a great measure owing to the superior degree of purity of 

 our common element at that time. 



From what is already related it appears, that the difference between tiie best 

 atmospheric air I have yet found and the sea air, as I found it by the first 

 examination on the spot where chance carried me, is as Ql to 100, the less 

 number indicating the best quality. Now as I found the sea air of such a pure 

 quality so near land, I thought it might, with some degree of probability, be 

 expected, that the common air, at a distance from land, would prove of a still 

 superior quality; for I could hardly believe, that in the first trial, made without 

 choice of place or time, I had just hit on a time and a place where the sea air is 

 of the first quality. 



I would have repeated the same experiment next day, November 4, when we 

 were in the middle of the channel between the English coast and Ostend; but 

 the motion of the ship, which was very great, made it impracticable. Not 

 entirely however to lose the opportunity which the voyage afforded me, I filled 

 3 phials, made on purpose for such use, with air, when we were in the middle 

 of the sea. I kept these bottles shut till next day, November 5, when I 

 examined the air confined in them at Ostend, and found it of an inferior quality 

 to that which I had tried on the 3d of November, in the mouth of the Thames; 

 for 1 measure of it with 1 of nitrous air occupied, in 3 different trials, og? . I 

 found the common air at Ostend near as good the same day at 10 in the morning, 

 the weather being cloudy, for 1 measure of it with 1 of nitrous air occupied 

 098. In the afternoon, the weather being very rainy, the common air of the 

 place was become worse, though still of a very good quality; for 1 measure of 

 it with 1 of nitrous air occupied 1 00, or exactly one measure. 



About 5 in the evening, the weather continuing rainy, and the wind blowing 

 at that time very hard from the sea, I went to the sea-shore on purpose to gather 

 in a phial, fitted for the purpose, the sea-air just as it blew towards the land. 

 When I had got it I went immediately home, and put it directly to the nitrous 

 test. I found it, by several trials, of such good quality, that it was nearly as 

 good as that which I had met with in the mouth of the Thames; for 1 measure 

 of it with 1 of nitrous air occupied O94 and 095, whereas the common air of 

 the inn was somewhat of an inferior quality, though still remarkably pure; for 1 

 measure of it with 1 of nitrous occupied O97 in 5 repeated trials. 



As the difference in the quality of the sea air examined on the spot in the 

 mouth of the Thames, Nov. 3, and that which I gathered in the middle of the 

 sea in rainy and windy weather, was so remarkable, I suspected the reason of this 

 difFerence to be, that the air, put to the test Nov. 3d, had been exposed during 

 several days to the influence of the sea without any mixture of land air, as it 



