340 Reciprocating Magnetic Attraction. 



joicings. A late article on the subject which accords in its facts 

 with other statements which I have, contains the following statements. 



" ' The whole number of steam boats which have been built upon 

 the western waters is about three hundred seventy five. Some of 

 them are of five hundred tons burden, and from that down to one 

 hundred, and their average not over two hundred tons. The num- 

 ber now in commission is something over two hundred. Their an- 

 nual expense for fuel is estimated at one million one hundred and 

 eighty one thousand dollars, and the other expenses at one million 

 three hundred thousand, making an aggregate of nearly two million 

 five hundred thousand dollars. 



" The value of steam navigation to the United States, and partic- 

 ularly to the great valley of Mississippi, is incalculable ; it defies the 

 power of calculation. We doubt whether the citizens of the United 

 States, who duly appreciate its importance, would be willing to part 

 with it for the amount of the debt of Great Britain of eight hundred 

 millions of pounds sterling. But for the introduction of steam navi- 

 gation into the United States, and its bringing, asit were into juxta 

 position, the extreme regions of her widely extended borders by 

 " conquering time and space," and but for its happy influence in pro- 

 moting international commerce, and social intercourse by the ties of 

 interests it creates, in a thousand different ways, the Atlantic and 

 Western states would soon have become alienated from each other, 

 and a separation would have been the consequence.' " 



Art. XVII. — On a Reciprocating motion produced by Magnetic 

 Attraction and Repidsion ; by Prof. Joseph Henry. 



TO THE EDITOR. 



Sir, — I have lately succeeded in producing motion in a litde ma- 

 chine by a power, which, I believe, has never before been applied 

 in mechanics— by magnetic attraction and repulsion. 



Not much importance, however, is attached to the invention, since 

 the atricle, in its present state, can only be considered a philosoph- 

 ical toy ; although, in the progress of discovery and invention, it is 

 not impossible that the same principle, or some modification of it on 

 a more extended scale, may hereafter be applied to some useful pur- 

 pose. But without reference to its practical utility, and only viewed 



