656 Miscellaneous. [Dec. 
For iron raised to a full red heat, (1,200°, according to Prinsep,) 1,436,990°— 
1,200° = 1,197.5 times, by using Prinsep’s degrees. 
For do. raised to an orange heat, 1650° P. 1,436,990—1,650—870 times by ditto. 
Reply to 3rd Question. 
IT almost fear to venture an opinion on the next question, but I should say, that 
the atmosphere is certainly, as the querist supposes, attracted, by the sun and 
moon, when in conjunction, or opposition, in the same manner, as are the tides of 
the ocean, or as any other light fluid, would be; but why the barometer is not 
sensibly affected, at these periods, I can only ask, whether he is sure that it is not 
so affected, or so much, at least, that a fair conjecture may be hazarded, that its 
rise is proportional to the increased height of the atmosphere, (if such indeed 
occur, at the time of high tides,) : our purpose will, therefore, be to see, whether the 
barometer can indicate this rise, or not, and if it do, to determine, what the 
amount of that difference is. 
May not one objection however be made, that will have a tendency to controvert 
this opinion, which is, that the force, exerted by the moon or sun, or both, to 
elevate the atmosphere, above its usual level, might, on account of the elasticity, 
or buoyancy of this body, destroy the additional weight, that would, otherwise, be 
added to it? In other words, would not the force of attraction, here supposed to 
cause the additional height, by the hold, (if I may say so,) that it has on the fluid, 
keep it in equilibrio, without adding any thing to the weight, by the increase of 
the part so added? 
This remark will not, of course, apply to water, but will it not to air, which is 
an elastic body ? If not, then I must resort to the first supposition, that there is a 
rise of the barometer, and that it is proportional to the increased height of the 
atmosphere, caused by the attraction of the sun and moon. 
If the height of the atmosphere were uniform, and of the same weight, as it is at 
the earth’s surface, pressing about 14#lbs. on the square inch, it would extend no 
farther than to the height of 5% miles, or thereabouts, (see Hurron’s Course, p. 
244, vol. ii.) whereas it reaches to between 40 and 50 miles, (the boundaries of 
twilight only included, the air being so thin and attenuated, beyond that distance, 
that its comparative weight amounts to almost nothing). 
Now, if the height of the atmosphere be increased, by any cause, (excluding 
heat, which would, however, have something to do with that increase, but has or 
has not to do with this investigation,) beyond the height of 45 miles, a propor- 
tional part must be reduced, in height, on the sides of the earth, which are at 
right angles to the horizon, acted upon by the sun and moon, to make up for 
this quantity, unless it be rarefied and of itself kept in equilibrio by attraction, as 
above supposed : it cannot be very great, but supposing it to be proportionally 
raised, as much as the sea, what will be the pressure gained, in this, upon one 
square inch, at the surface of the earth, and also, at what height will the baro- 
meter stand, in this case? 
Taking 122 feet, which is about the height of the tides, or what is added to the 
ocean, by the attraction of the sun and moon, either when in conjunction or oppo- 
sition, and assuming $ of a mile, or 1760 feet, as the average depth of the 
ocean, of which 123 feet is near the 138th part; by taking the 138th part of the 
atmosphere’s height of 45 miles, as above, we get .326087 parts of a mile for the ad- 
ditional height of the atmosphere, gained by the force of attraction, consequently, if 
45 miles press upon the surface, with a weight of 143 lbs. per square inch, 45.326,087 
