MEMOIR OF DANIEL TKEADWELL. 451 



each thread one inch,' and ' to make the threads of the female screws sensibly finer than those of 

 the male, to draw, by the shrink, the inner rings togetiier endwise.' The advantage of this form of 

 construction will appear in this : that by the rapid advance of the hoop to its place, the shrinkage 

 from cooling during its passage over the body will be avoided ; while the dividing of the inch space 

 of the spiral into several parts enables us to give a great bearing surface to very shallow threads. 

 Small fiplincs sliould be inserted under every hoop to prevent its turning by the recoil. 



"I give here a drawing of the threads as I would form them for a six-threaded screw. 



They have an .18 inch pitch, and a depth of .04 in., being .11 in. thick at the root or bot- 

 tom, and .07 in. in breadth upon the face. Threads of this shape may be more easily and 

 exactly made than any other, as a large part of the surfaces left by the Ijoi'ing and turning tools 

 requires no change from tiie screw tool, but remains and forms the fiat faces of both the male 

 and female screws. By this means the gauged sizes and i-equisite diameters of both the body 

 and the hoops are more easily ascertained and preserved, when the screw threads arc formed. 



" The depth of the threads given in tliis figure must be ample ; for, as the threads, when once 

 interlocked and in place, are kept in contact by the shrinkage of the hoops and the distension of 

 the gunpowder, the idea of the outer threads slipping and riding over the inner ones, like a loose 

 nut upon a screw bolt, is simply preposterous." 



In the summer of 1854 he made a voyage to Europe. Soon after his arrival there 

 the war began to rage in the Crimea, and he thought of bringing his invention before 

 the French government ; but as lie could not well arrange his engagements so as to stop 

 in Paris, he went to Italy. Reading there the accounts of the bursting of guns in the 

 Crimea, he determined to go bacli to Paris as soon as possible to propose his invention 

 of hooped guns to the French War Office, and addressed a letter to Marechal Vaillant, 

 Minister of War, stating that in 1845 he had manufactured for the United States guns 

 of wrought iron, and that he at the same time made a 32-pounder and sent it with the 

 aid of the French Consul in Boston as a present to the King of the French, and it was 

 then at the fort of Vincennes. He requested that a learned and intelligent officer 

 might be appointed to wliom he could communicate new and improved methods which 

 he had since devised. After waiting in Paris several weeks, and receiving no inti- 

 mation that an officer would call upon him, he went to London, and after three weeks 

 received a letter from a French officer who had been appointed to meet him. 



Professor Tread well on the receipt of this letter would have gone immediately to 

 Paris and communicated his invention to the French government, but feared that the 

 delay might occasion the loss of his invention in this country, as public attention was 

 then turned both in Europe and America to improvements in cannon. He therefore 

 concluded to take out the patent in America, and to that end sat down in his lodgings 

 in London, and, without the aid of legal advice or books, di'ew up the specifications of 

 his invention as it appears in the first patent issued. 



