280 MR. LUKE HOWARD ON THE INFLUENCE OF THE MOON'S DECLINATION, ETC. 



shown, as it is found to operate through a cycle of eighteen years. In these, the mean 

 weight of our atmosphere increases through the fore-part of the period ; and, having 

 kept for a year at the maximum it has attained, decreases again through the remain- 

 ing years to a minimum ; about which there seems to be some fluctuation, before the 

 mean begins to rise again. 



This result is brought out in different ways by all the averages upon years ; and it 

 pervades, though with less of uniformity, those upon the quarter periods or weeks of 

 declination. The study of these, with a view to theory, rude and imperfect as they are, 

 may become, I would willingly hope, an occupation for those more capable and better 

 prepared than myself to grapple with the subject. 



L. H. 



February 3, 1841. 



