MECHANICS AND USEFUL ARTS. 87 



and with but little taper, so to fit the hole, often sixteen inches deep, as tight 

 at the bottom as upon the outside. 



As the wood is hard and stringy, it is not an easy matter to make all the 

 pins equally good, even by the most skillful workmen ; and by those that are 

 careless they are frequently made so tapering that one half of a lot are fre- 

 quently found to be worthless, the butts only filling the hole, and being wedge- 

 shaped, very apt to check the plank. 



To obviate these difficulties the common turning-lathe has been employed, 

 and large quantities of round tree-nails have been used. The lathe made 

 them true, and timber could be worked by that means that could not be 

 shaved by hand ; but there was another difficulty that could not be overcome 

 the tree-nails made in the lathe were round, and could not, like the eight 

 square ones, be driven into a hole actually smaller than the diameter of the 

 pin, and when forced in by the hardest driving the round pins could be driven 

 out. It is a consideration of the most important kind, that, when driven 

 home, the tree-nail should be absolutely immovable, as many a ship has been 

 lost by "starting a butt;" that is, drawing the fastening. A well made eight 

 square tree-nail being the one thing needed in ship-building more than any 

 other, a machine that would do the work in a rapid, economical manner, both 

 of time and timber, it was thought by ship-builders would be one of the most 

 important mechanical inventions of the age. Most of those who thought upon 

 the subject said the thing was impossible. A man by the name of Fitzgerald, 

 of New York (since deceased), by nature an inventor, being told what was 

 wanted, said at once, It can be done, and at once set himself to work and 

 completed a machine, which is now in successful operation. 



The machine is about 4 feet long and 3 feet high, iron frame, the cutters eight 

 in number, driven by a band and pulley. The stick in its rough square form 

 is held up to the cutters a moment, and then is taken into the feed wheels, 

 which carry it forward, each cutter revolving and cutting one of the eight 

 sides, the taper, or variation in size, being so regulated by a cam, that the 

 tree-nail may be cut with a true taper from end to end, or made smallest in 

 the middle. It is found best to run them through two machines, the first 

 shaping, and the second finishing, at the rate of about 430 feet an hour. The 

 length varies from 16 to 24 inches, and size from to 1^- inches diameter. 

 "Whatever the size or shape, whether tapering or straight, the cam being set 

 for the particular size desired, every one must inevitably be of the same exact 

 form, and such is their perfection, that one has never been known to check a 

 plank, and they can be driven into holes a sixteenth of an inch less than the 

 pin, the eight corners pressing into the wood, and making a water-tight joint 

 at the extreme end. It is found, too, that they drive extremely easy, and 

 that it is absolutely impossible to start one of them back. 



MACHINE FOR QUARKYING SLATE. 



Slate has heretofore been all cut out in quarries by hand labor. The 

 workmen with picks cut grooves in the rock to the depth required, and then 

 the slate comes off in thin layers the size of the space between the cut grooves, 



