ENGINEERING. 299 



ward current required to make it rain, just as it commonly rains after any great 

 fire, or the eruption of a volcano, or a battle. 



Espy visited Princeton to confer with Prof. Henry. I was present at the 

 interview. Henry, while he thought Espy's main principle quite correct, got 

 very much out of patience with him for several hasty conclusions from statements 

 which, to Henry's cautious, scientific mind, did not seem at all conclusive. ^ 

 After he was gone, Henry chalked out the plan which he afterward, with the co- 

 operation of Guyot and other able men, so successfully carried into execution, of 

 simultaneous observations all over the country, and a daily chart of highest and 

 lowest pressures, and other things about which my memory is less distinct. As 

 everybody knows now, it is the traveling of these lines from west to east, at an 

 average of about thirty miles an hour, that enables the weather predictions to be 

 made. 



Our rapid progress involves the frequent undoing of what has only recently 

 been done in the most costly manner. We have seen expensive buildings erected 

 in the City of New York, and then in two or three years torn down to give way 

 to something greater or different. The Alleghany Portage Railroad, of which 

 my brother, Sylvester Welch, was chief engineer, W. Milnor Roberts being one 

 of his assistants, was considered for some years one of the wonders of the world ; 

 the improvements in the locomotive and the increased strength of the rails after- 

 ward enabled engines to cross the Alleghany without the incUned planes used on 

 that road, and that splendid work, on which so much thought had been expend- 

 ed, was torn up. It is folly to build for the far future. 



This reminds me that in a paper written 1829, r^ad before this society two or 

 three years ago. Mr. Moncure Robinson estimated that the tonnage over the Al- 

 leghany Mountains at that point might in time reach 30,000 tons per annum. I 

 suppose that the tonnage now over the mountain, on the Pennsylvania railroad, 

 exceeds six millions. 



One of the bold and remarkable works of the day is the submarine sewer at 

 Boston, to carry the sewage under an arm of the harbor and across an island far 

 to the seaward. They have discovered, what unfortunately many others have 

 not, that little is gained by emptying sewage into a harbor or into a small river, 

 and so transferring the nuisance from one point to another, or distributing it all 

 over. 



Sanitary engineers have been contending each for his own favorite system of 

 sewering and draining cities. Mr. Hering, in his paper read at the convention 

 at Montreal, impressed upon us that no one system is absolutely good or bad, 

 but either is good when adapted to the circumstances, and bad when it is not. 

 Municipal corporations often think that the remedy for unhealthiness is, of course, 

 sewerage, just as some doctors in old times gave their patients calomel without 



1 My attentioij was drawn to this subject by the conference between Espy and Henry, and while travel- 

 ling in Ireland, I asked my very bright, and on the subjects within his range, intelligent car driver, which way 

 the storms there came from ? Evidently he had never thought on that subject, but, adopting on the instant a 

 meteorological creed, answered quick as thought: " The storms, sir, come from whichever way the Lord Al- 

 mighty chooses to send them." 



