within the Cataract of Niagara. 367 



fore I could obtain even a tolerable reading, for the water 

 flowed over my brows, like a thick veil, threatening to wash 

 the whole affair, philosophers and all, into the basin below. 

 I managed, however, after some minutes delay, to make a 

 shelf or spout with my hand, which served to carry the water 

 clear of that part of the instrument which I wished to look 

 at, and also to leave my eyes comparatively free. I now 

 satisfied myself, by repeated trials, that the surface of the 

 mercurial column, did not rise higher than 29.72. It was 

 sometimes at 29.70, and may have vibrated two or three 

 hundredths of an inch. 



This station was about ten or twelve feet lower than the 

 external ones, and therefore I should have expected a slight 

 rise in the mercury ; but I do not pretend to have read off the 

 scale, to any great nicety ; though I feel quite confident, of 

 having succeeded in ascertaining, that there was no sensible 

 difference between the elasticity of the air at the station on 

 the outside of the falls, and at that, one hundred and fifty-three 

 feet within them. 



I now put the instrument up, and having walked back to- 

 wards the mouth of this wonderful cave, about thirty feet, tried 

 the experiment again. The mercury stood now at 29.68, or 

 at 29.70, as near as I could observe it. On coming again into 

 the open air, I took the barometer to one of the first stations, 

 but was much disappointed though I cannot say, surprised, to 

 observe it full of air and water, and consequently, for the time, 

 quite destroyed. My only surprise indeed was that under 

 such circumstances, the air and water were not sooner forced 

 in. But I have no doubt that the two experiments on the out» 

 side, as well as the two within the sheet of water, were made 

 by the instrument, when it was in a correct state ; though I 

 do not deny, that it would have been more satisfactory to 

 have verified this, by repeating the observations at the first 

 stations. 



On mentioning these results to the contending parties in 

 the controversy, both sides asked me the same question. 

 " How then, do you account for the difficulty of breathing, 

 which all persons experience, who go behind the sheet of 

 water ?" To which I replied, " that if any one were exposed 

 to the spouts of half a dozen fire engines, playing full in his 

 face, at the distance of a few yards, his respiration could not 

 be quite free ; and for my part I conceived that this rough dis- 

 cipline would be equally comfortable in other respects, and 



