d6 Mr Henry Meikle's Remarks and Experiments 



the effect was considerably less, especially when the sides of the 

 bottle were dry : as the depression, in that case, was only 53° — 

 41°.2=rll.°8 ; and by repeatedly wetting the sides with acid, as 

 was done with the small flask, the utmost effect was only 53°. 1 

 — 40°.4=12°.7. But by suspending the thermometers, and 

 making them vibrate near the bottom as before, the depression 

 reached 53° — 39°.9=:13°.l, as in the former experiments ; though 

 such perfect coincidence may have been a little accidental. 



In the small flask again, with acid only in its bottom, and its 

 sides dry, the result was 52°.6— 42°.4=10°.2. To do justice to 

 such experiments, a considerable time must be spent on them ; 

 for though, in the open air, the wet thermometer soon attain its 

 utmost depression, yet, in a close vessel, particularly a small one, 

 it proceeds with extreme slowness, and at a retarded rate. Those, 

 who are not aware of this circumstance, are apt to obtain de- 

 ficient results. Motion, in the free air, hastens the depression, 

 but unless it be rapid, it scarcely affects its amount. On the 

 other hand, a dry thermometer rises a little, by being moved 

 swiftly through the air. 



Wishing to try the effects of different atmosphelic pf^ssures 

 on the depression, I placed the double thermometer over a broad 

 saucer of sulphuric acid on the plate of an air-pump, and covered 

 the whole with a receiver. The following are the results at dif- 

 ferent pressures : 



The first column is the barometric pressure in inches ; the 

 second the Fahrenheit temperature of the dry thermometer ; the 

 third that of the moist, and the fourth their difference or the de- 

 pression *. 



• Experiments of this sort take such a length of time, that I only, at first, 

 intended to have tried three different pressures, the 1st, 2d, and 5th, differ- 

 ing about ten inches, but before concluding, I added the other two, to come 

 close upon the freezing point ; though both, as we shall shortly see, should, 

 when corrected, be above 32°. 



