490 



MEMOIR OF DANIEL TREADWELL. 



to the Departments, and I was struck in some instances with the extravagant and unscrupulous 

 eagerness of common persons who thought they had discovered a way of getting rich. 



I hope the decision of the court in your prosecutions of the Parrotts will award you — what 

 you value more than money — -the honor and merit of being the first to conceive of, and to 

 employ, coiled spiral rings in the construction of wrought iron guns. 



_ a>w -_i a a na _ ■ m 



most cordially to Mrs. Treadwell, and believe me 



faithful friend. 



II 



>> 



Professor Winlock of the Harvard College Observatory, at a meeting of the Ameri- 

 can Academy, September, 1866, read a paper by Professor Treadwell " On the Com- 

 parative Strength of Cannon of Modern Construction. 



The standard gun is assumed to be the old 32-pounder, with a charge of eight 

 pounds of powder and one shot, with an initial velocity of 1,600 feet a second ; the 

 standard unit of force is taken as the height to which the shot would rise in vacuo, or 



o 



40,000 feet ; this multiplied by the weight of the shot, 32 pounds, gives 1,280,000 

 pounds raised one foot in one second as the measure of force. 



To determine the strength of the gun, as well as the force of the shot : " H 



r> 



already seen that our standard 32-pound shot has a force of 1,280,000 pounds raised 

 one foot, if we divide this product representing the strength of the whole gun by 

 the weight of the metal of which the gun is made up in pounds, we shall obtain the 

 strength or work which may be done by one pound of the metal of which the gun is 

 constituted. We shall find the result of this computation (the weight of our standard 

 32-pounder being 7,500 pounds) to be ( Hrf" = 171) 171 pounds in shot raised 

 one foot by every pound of metal which forms the body of our standard gun." 



This computation, applied to the Dahlgren, Rodman, and Armstrong guns, gives 

 the following results. The number of pounds of shot raised one foot by each pound 

 weight of the gun is, for the Dahlgren, 144.7 pounds; the Rodman, 125; the Arm- 



g, 372.8 



To Dr. William Sweetser. 



Cambridge, November 4, 18G8 



My dear old Friend, — ! received your most kind letter early in September 



from 



A 



letter from you is always most welcome to me. It is especially so now, when oppressed with 



infirmities 



am 



make light of the D 



can walk at pleasure, and, as I trust, have the advantage of a good appetite for food, and the enjoy- 

 ment and vigor that flow from indulging it. I congratulate you also on the philosophical quiet 



For correction of error as to Armstrong gun, — 261 instead of 372.8, — see Proceedings of the American 

 my, September 11, I860. Vol. VII. o. 412. 



