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XII. On the hest Means for conduclwg mefeorological Obser- 

 vations in different, Places and Climates, so as to produce 

 some Uniformity in the Modes of obtaining and summing np 

 the Results. By Luke Howard, £59. 



To Mr. Tilloch. 



My old and respected Friend, — 1 have to thank thee for 

 the care and delivery of a letter on Meteorological Subjects, ad- 

 dressed to me from Italy; and in doing this to claim a little 

 space in the pages of the Philosophical Magazine, so often use- 

 fully devoted to this branch of science, for the purpose of giving 

 publicity both to the most material parts of the letter, and to a 

 few observations I shall have to make upon it, and which I have 

 no doubt will by this means promptly reach its author. 



The gentleman who favours me with this communication, and 

 who subscribes himself" Castei.lani, Inspecteur dans le Corps 

 de Ponts et Chauss^es a Turin," has been led by the duties of 

 his profession to pay a regular attention to meteorological ob'^er- 

 vatious; and in attempting to compare his own with those of 

 other observers, in distant climates, has been stopped by the 

 obstacle so generally experienced by the cultivators of this in- 

 fant science, the variety which prevails in the mode of obtain- 

 ing and summing 7ip ntsulls. As it is not at all probable that 

 men of science in different countries will long continue to sub- 

 mit to the glaring absurdity of being thus, as it were, barbarians 

 to each other, in a branch of their common pursuits vviiich pro- 

 mises, by due culture, to become both fruitful and respectable, 

 I think it but justice to this gentleman here to state the prin- 

 ciples on which he thinks the common system should be founded c 

 which are these : 



^The Meteorological year to begin with the vernal equinox : 

 by this means, the six summer months are made to form the 

 firit division, and the six winter months the second ; for the 

 purpose doubtless, though he does not mention it, of contrasting 

 the mean temperature, rain, ike. of the two seasons; and of 

 each of them with the same in other years. 



The svbdiuisions to be of le7i days each. The author thinks 

 a mean result founded on the month comprehends too many of 

 the daily observations, and that of the wet*^, too few; while re- 

 sults taken on every ten davs would, in his opinion, give the 

 course of temperature, in particular, in a more perspicuous man- 

 ner. Each of the four seasons in this case would consist (with 

 the necessary intercalary additions) oi nine decades of days. 



A more important oI)jcct still with him is, the proper division 

 of the day of 21 hours: for ho thirdvo wc lose much ill makinij 



Vol. 67. No. 271. /-W. 1821. h our 



