86 



NEW YORK STATE MUSEUM 



Where x is the unknown special coefficient of deficiency due to 

 wind at that altitude — that is to say, having two gage catches, 

 c x and c 2 for the two altitudes, B. t and H 2 — we obtain the true 

 rainfall (R) by the formulas: 



c=(l—x^R) R ; and (2) 



c==(l-xVB 2 ) R. (3) 



whence, 



E - Gl ^m^7w 1=G ^ -7!f— <*-^ (4) 



v 7 B, 



If c x and Hj relate to the lower gage, we shall generally have 

 r a and Hj <H 2 , and the coefficient n will be a positive fraction, 

 for value of which, for such combinations as may easily occur in 

 practice, a table is given in the paper. 



It is evident then, without special discussion, that nearly all 

 rainfall measurements thus far made in the United States are 

 only approximations, and that while they remain in this state to 

 carry them out to more than one decimal place is an unnecessary 

 refinement. 



Determination of minimum rainfall. The writer has spent con- 

 siderable time in an attempt to determine about what the mini- 

 mum rainfall at any particular station may be expected to be; or, 

 rather, he has endeavored to ascertain the relation between the 

 minimum rainfall and the maximum. In the course of this quest 

 he has examined practically all the records in the State of New 

 York, as well as many records in New Jersey, Pennsylvania, 

 Michigan, Illinois, Nebraska, Colorado, and Wyoming, as well as 

 in Canada. As a general rule, to which there are some excep- 

 tions, the minimum rainfall may be placed at about one-half of 

 the maximum. That is, if the maximum rainfall at a given 

 station is about 50 inches, the minimum will be in the vicinity of 

 20 to 25 inches. In some cases the minimum will be not more 

 than one-third of the maximum, or even somewhat less than one- 

 third; occasionally, not more than one-quarter. It is not in- 

 tended, however, to lay this down as an absolutely universal rule, 

 but rather, for the present, as a somewhat imperfect guide. As a 



