1 42 O71 the Barometer. 



Comes nyore complicated, in consequence of its situafJorj 

 between the two fornler ; being occasionally influenced by 

 each of them, separately or conjointly. 



There seems to be a kind of habit in the weather, as in 

 other cases : thus, towards the close of a series of dri/ 

 weather, several efforts are apparently made towards a series 

 of rainy iveather, before it actually sets in; and hiversehj. 



With respect to the difference of the weafher, which I 

 have presumed lukts place during the increase and wave 

 of the moon ; I would account for it on a supposition that 

 at each conjunction of the moon with the sun, or the time 

 of the new moony as it is called^ there may be a kind of dis- 

 position, as it were, i'oT c/cxr/Jyiiig the atmosphere, or re?io- 

 vation of fair weather-, and vice versa, at the moon's op- 

 position, or J'u/l moan ; and the reason why this change 

 does not actually take place until about the third or fourth 

 day after each change of the moon, because, as I have stated 

 before, the former habit of the weather is not till then 

 entirely conquered. 



The atmosphere becoming drier, as indicated by the hy- 

 grometer, indicates a disposition for Juir weather, and vice 

 versa. 



A cold, dry, and serene state of the atmosphere is most 

 favourable for barometrical measurements. 



The limit, or boundary of the atmosphere, terminates 

 where the expansive force or power of the air, upwards, or 

 from the earth's surface, is completely overcome by the 

 force or power of gravitation downwards, or towards the 

 earth's surface, which is estimated at about 44 or 45 miles*. 

 A pint measure of air, when the barometer is at 29'- in 

 England, weighs eight grains, or a gallon 64 grains; but 

 near the poles somewhat more ; and at the EauATOR 

 somewhat less. This variation in the weight of the air, in the 

 different parts of the world, is ascribed to a difference in 

 the height of the atmosphere; by which it happens, that the 

 air near the surface of the earth, at different places, differs 

 in density ; the pressure or weight of the incumbent at- 

 mosphere being the same. The atmosphere is presumed 

 to extend highest at the equator, and to be lowest at the 

 poles; in consequence of a greater degree of centrifugal 

 force and heat at the equator. 



The barometer, cceteris paribus, stands higher in w inter 

 than in summer, in consequence of the greater condensa- 

 tion of the air, from cold, at that season. 



• The atmosphere, it is computed, would extend only to about 5§ miles 

 in height, if it were so compressed, that its density throughout should 

 equal its degree of density near the surface of (he earth. 



The 



