The machines for making the pins. As we are not able to present our readers with drawings of these machines, we have but little more to say of them 1 than was mentioned in our list of the machines. The iron pins are forged between swages, by two men, in the usual way, being cylinders, except a small length atthe end, which .is left square for the pur pose of holding in one of the cheeks of the block, to prevent the pin from turning round. These pins being centered by a simple tool, are carried to a lathe of 'immense strength. It has a short mandrel, and a back centre to support the extreme end of the pin. It has also a long slider fixed parallel to the pin, and provided with a rod similar to g in the last machine, which detaches the movement of the screw, when the whole length of the pin is turned. The holder of the tool has a small table fixed to it, which carries a vessel containing cold water, and provided with a cock, from which a continued stream of this water falls upon the tool. This is an essential provision, as the great strain of turning so large a piece of iron would certainly heat and soften the tool, which is of an excellent form for the purpose, being a cylindrical piece of steel cut obliquely, so as to form an elliptic • section, the highest point of which forms the cutting edge. The tool is held in the same manner as the gonge'of the shaping engine.
After being turned, the pins in a curious machine. It has a revolving spindle, placed vertically. The pin is fixed at the end of this, and, as it turns round, is forced down between three dies, or smooth pieces of hard steel, highly polished. These are fitted in a frame, and have screws behind them, by which they can be thrust forwards against the pin, to grasp it tight, and" make such a pressure as will burnish down all the spiral scorings left by the turning lathe. The dies are immersed in oil to faci.
litate the operation, and prevent the dies from heat ing. The pins after this process are highly polished and fit for use.
Having now explained the mode of making all the parts of a block, its shell, sheave, and pin, it only re mains to put them together, in which operation there is nothing singular or worthy of detail.
We shall conclude this article by observing, that these machines, with alterations, might be adapted to many useful purposes in the mechanical arts ; particu larly the mortising machine, which would be a most excellent tool for forming mortises in any pieces of work where a great number of similar pieces are re quired, so as to render it worth while to erect such an engine. Any person who has had the patience to stand by a carpenter while performing the tedious and laborious process of mortising through a large beam of wood, will judge of the importance of a ma chine which makes from 110 to 150 strokes per mi nute, and cuts at every stroke a chip as thick as pasteboard, with the most perfect accuracy. (J. •.) We are proud in having had it in our power to pre sent our readers with the first account of these valu able machines that has yet been given to the world ; and we are fully compensated by this feeling, for the great labour and expense by which this object has been obtained. We hope, in the course of our work, to lay before our readers, other proofs of the great mechanical genius of Mr Brnnell. (Ea.)