6g6 VHILOSOPHICAL TRANSACTIONS. [aNNO 1780. 



had been remarkably calm all that time; and that the air gathered on the sea in 

 windy weather was mixed with air driven from the land by the wmd, and incor- 

 porated with the sea air. This suspicion was afterwards strengthened when I 

 found the air gathered at the sea shore, on the evening of Nov. 3, near as good 

 as that which I gathered on a fair day in the mouth of the Thames, Nov. 3 ; for 

 the wind being n. w. the air driven on the coast was to be considered as true sea 

 air, without any mixture of land air. 



But after making up my mind about the difference of the above experiments, 

 a doubt rose about a circumstance to which this difference might have been owing, 

 at least in some measure; the circumstance I mean was this: I had made use of 

 sea-water for the experiment on Nov. 3, whereas I had made use of pump-water 

 in examining the sea air kept in bottles at Ostend. I thought I had no right to 

 draw any conclusion from the fact till I was convinced that the making this ex- 

 periment in common or in sea-water would make no difference in the result. 

 This consideration made me stay one day longer at Ostend, on purpose to satisfy 

 my mind on this head, lest I should never find another opportunity of doing it. 

 I immediately ordered a pail full of sea-water to be brought to my lodging, and 

 made several comparative trials with atmospheric air in common water and in this 

 sea-water; but I could not observe any real difference in the result. Thus ail 

 degree of suspicion about the difference of the result from this cause was now at 

 an end. 



There now only remained some little suspicion that the air gathered on the 

 sea, and kept in phials, might have undergone some alteration; this might have 

 been the case, as I had found in some former experiments made in England, that 

 air kept in bottles was sometimes liable to alterations, which I think is partly to 

 be ascribed to the difficulty of finding bottles so well secured by a ground stopper 

 as to shutout every communication with the external air, and partly perhaps to 

 the nature of air, which is not in itself an unalterable substance, as I have at- 

 tempted to prove in my book on Vegetables, p. 107: in the present case how- 

 ever, I rather incline to think, that the reason why the air, gathered in rainy 

 and windy weather on the sea, was found of an inferior quality, is to be ascribed 

 chiefly to the land air being driven by the wind on the sea, and thus to the mix- 

 ture of both airs. 



Nov. 6, about 9 in the morning, the weather being cold, windy, and cloudy, 

 I again put the common air of Ostend, which I gathered in my inn, to the test, 

 and found it of near as good a quality as that in the mouth of the Thames; for 

 1 measure of it with 1 of nitrous air occupied 0Q4^ in 3 repeated trials. The 

 same morning, about 1 1, the wind blowing very hard from the sea, I went to 

 the shore on purpose to gather some air just as it came from the sea. I foimd 

 its quality inferior to that which I had examined 2 hours before, though still su- 



