108 Mr Meiklc 07i the Theort/ of the 



admit the correctness of such a conclusion, would be taking for 

 granted, that the fluidity and the mutual action of the particles 

 on each other do not affect the result. Mr Tredgold has lately 

 shewn, that Newton''s overlooking this circumstance, in investi- 

 gating the laws of the resistance of fluids, has led him and his 

 followers into very erroneous conclusions ; and, by hastily pur- 

 suing a similar path, we should have reason to fear the like 

 consequences. It was probably considerations of this nature 

 which induced Mr Leslie not to apply the ordinary mode of es- 

 timating the centrifugal force of solids to the fluid atmosphere. 



There is, however, a very important circumstance connected 

 with the centrifugal force of wind, which does not appear to have 

 been yet attended to, and which throws a very different hght 

 on the subject, though still adding greatly to the probability 

 that the barometer has to do with the centrifugal force. The 

 circumstance to which I allude is, that the curvilinear motion of 

 wind, describing a circle about the earth, in place of always 

 lowering- the barometer, ought frequently to augment the pres- 

 sure of the atmosphere, and consequently to raise the barometer. 

 At first sight, this may seem paradoxical enough, if not tho- 

 roughly absurd ; but to solve it, we have only to consider, that, 

 when the wind is from the east, its diurnal motion round the 

 eartVs axis is thereby lessened, its centrifugal force will be of 

 course weakened ; and so the air will be more at liberty to gra- 

 vitate or press freely on the earth's surface, and consequent- 

 ly to raise the barometer. Westerly winds, on the contrary, 

 by conspiring with the diurnal motion, increase the centri- 

 fugal force, and diminish the pressure. Hence the reason why 

 the barometer is commonly lower with westerly winds than east- 

 erly. Such difference of effects in opposite winds, so far as 

 centrifugal force is concerned, will become smaller as the lati- 

 tude increases, and the currents approach nearer to the direction 

 of the meridian. But cold air from a higher latitude raises the 

 barometer, from its being heavier than the comparatively moist 

 and warmer air of a lower latitude. Hence, from the combina- 

 tion of these two causes, the barometer in this country is usually 

 hiffhest with a north-east, and lowest with a south-west wind. 



But the effects just mentioned are liable to be modified or 

 overruled, by various causes of a less general nature. The de- 



