On land and sea AIR. 269 



To thefe experiments I will fubjoin thofe I made on the 

 ocean during a paflage from Bourdeaux to Philadelphia. 

 It appeared to me preferable to conned: them in the form 

 of a table, as thereby I fhould avoid aneedlefs repetition ; 

 and place before the reader a fliort though accurate view 

 of all the experiments at the fame time. 



The experiments 1 performed on the River Elk and 

 Bay of Chefapeak pcrfedlly agree with each other ; and 

 the rcfult was the fame with thofe performed on the 7th 

 of July Sscc. as mentioned in the table. The wind blew 

 from the North and the fky was partially cloudy. They 

 were performed in Auguft lafl. 



My experiments at fca fufficiently prove that the at- 

 mofphere is confiderably purer there than it is on land. 

 Though there are fome trlHing differences in the refults 

 of feveral experiments, 1 have no reafon to believe that 

 they were owing to the different fituation in point of la- 

 titude or longitude in which they were performed. I 

 can form no fyftem refpeding fuch variations. Winds, 

 temperature, rain, &c. do not feem to have produced 

 them. As they did not obferve any regularity in their 

 occurrence, they may perhaps be attributed to certain un- 

 perceived errors which are unavoidably attendant on fuch 

 trials. 



That the air at fea fhould appear nearly of the fame 

 purity in different latitudes does by no means aftonifii 

 me ; for if land air has certain matters mixed with it 

 they are perhaps abforbed ; and if my fuppofition be true, 

 that the influence of the Sun's rays on the water tends to 

 encreafe its purity, the opinion 1 enter ain is not furprif- 

 ing. For when once purified, there are perhaps none, or 

 few caufes to render the air noxious after it is wafted from 

 our towns and cities over a large body of water. 



It occurred to me that probably the purity of the air 



at fea varied at different periods of the day : to fitisfy 



M m myfelf 



