38 THE POPULAR SCIENCE MONTHLY. 



destructive. But all these instances are peculiarities singled out from 

 a variety of items, highly interesting to any one contemplating either 

 a temporary or permanent residence in a place new to him. The 

 storms, the rain, and the snow he has to encounter ; the average hu- 

 midity and tenuity of the air he has to breathe; the variety and char- 

 acter of the winds that are to blow upon him ; the mean and extreme 

 of the daily, monthly, and yearly temperature to which he will be sub- 

 jected ; the relative number of cloudy and clear days — all this, con- 

 stituting the climate of a place, should be known to one ere he hazards 

 his comfort, his good feeling, or, it may be, his health, by a change 

 of residence. And it is probable that, with the great number of ob- 

 servers noAV carefully noting and recording these items in various 

 cities, the day is not far distant when their laborious experience of 

 long years will be classified, reduced, and published in such a compen- 

 dious form, that a stranger to any given place may, by half an hour's 

 study of this publication, inform himself correctly as to its climate. 



The solution of the third phase of the problem is the one produc- 

 tive of most immediate benefit to all, how much soever their callings 

 may differ ; and this universal interest warrants my stating its condi- 

 tions more at length than I have done with the other two. This phase 

 may be likened unto an algebraic equation — a combination of known 

 and unknown quantities, which, being operated uj)on according to cer- 

 tain rules, gives a desired result. 



First, to determine the known quantities, a variety of instruments 

 must be read and recorded at stated periods. These are, anemometers, 

 to indicate the direction and velocity of the wind ; barometers, to mea- 

 sure the pressure of the air ; and hygrometers, its humidity. Suppose 

 sets of these, standard in quality, to be furnished a corps of trained 

 observers stationed at various points throughout a given area, say a 

 thousand square miles ; let each observer note his instruments at pre- 

 determined hours, or, better, let the observation be automatic and con- 

 tinuous, which is now often done by means of mechanical contrivances; 

 let a network of telegraphy connect all the stations with some central 

 point : then, at any moment he wishes, a person at this point can as- 

 certain the prevailing weather all over the area, or, in other words, 

 the known quantities of his equation. Now, the atmosphere that en- 

 circles our globe is but an ocean of less density than the watery ele- 

 ment that surges upon its surface ; like that, it moves, contracts, and 

 expands according to well-known physical laws, and these laws consti- 

 tute the rules whereby the person at the central station operates on 

 his known quantities, solves the equation, and obtains for a result the 

 forecast of the weather for the next few hours. 



Having a due regard for the conformation of the ground over 

 which his prognostics extend, he well knows that, according to the 

 relative variation of pressure, temperature, and moisture, there will be 

 a corresponding variability of weather : that if the pressure is great 



