43 



em margin of the United States; and to render our system complete, re- 

 quires the co-operation of the British government to extend the observa- 

 tions to the entire region of Hudson's bay. 



If we merely wished to embrace in our observations the area of a storm 

 for a single hour, then the interval between the Mississippi and the Atlan- 

 tic would ordinarily be sufficient. But we could not thus expect to dis- 

 cover the origin of a storm. We must trace it in its progress from its com- 

 mencement to its greatest violence, and thence to its decline. By observing 

 under what circitinstances it takes its rise, we may hope to be able to dis- 

 cover the cause of its activity. We should therefore aim to trace every 

 storm from its origin to its close. At the ordinary rate of progress a great 

 storm would travel from the Rocky mountains to the Atlantic in two days. 

 What influence this range of mountains may have upon our storms is un- 

 known, except from conjecture. We cannot suppose that a storm could 

 travel from the Pacific to the Atlantic without experiencing some modifi- 

 cation in passing over a range of mountains rising into the region of per- 

 petual snow. What this modification is, can be determined by corres- 

 ponding observations on both sides of the mountain. I therefore conclude 

 that it is important to embrace in our system of observations the entire 

 continent from the Pacific to the Atlantic, and from the gulf of Mexico to 

 the northern shore of Hudson's bay. 



2. At what distance from each other should stations of observation be 

 selected ? 



If we were investigating the phenomena of a summer shower, it would 

 be indispensable to have stations at very short distances from each other; 

 but in winter storms this is less important. I consider it, however, desira- 

 ble to have stations at intervals of fifty miles from each other, and such 

 might probably be obtained in the more thickly settled parts of the United 

 States. In other parts of the country this would be impracticable; but I 

 would strive to obtain at least one station for every hundred miles square. 

 At this rate we should need about three hundred observers for the United 

 States. It is not doubted that this number might be obtained; indeed, we 

 have well nigh this number already, but, unfortunately, they are very une- 

 qually scattered over the country. 



3. What materials have we to depend upon, and what is wanting to 

 complete the plan of one observer to every hundred miles square ? 



We have the government observations at the military posts, now 57 in 

 number. We have observations from 41 academies in the State of New 

 York, and 2-5 stations in Pennsylvania. Then we have borometric obser- 

 vations from about 40 other individuals scattered promiscuously over the 

 country; and thermometric observations from about 20 others. There is, 



