190 



STATICAL BLOW PIPE. 



We have made a great many more experiments with the 

 explosive compound j but as this communication is already of 

 considerable length, we shall reserve the account of them for 

 the next number of your Journal . 



We are, Sir, 

 Your most obedient, humble Servants, 



II. PORRET, Jun. 

 W.WILSON. 

 London, l6th Feb. 1813. RUPERT KIRK. 



Instruments 

 having fluid 

 packing. 



Description 

 Bt tLe blow 

 pipe. 



vi. 



A Statical Blow Pipe, with Remarks ly C. L. 



THE mercurial pump of Haskins, described by Desaguliers 

 in his lectures j the water bellows of Hornblower in your 

 1st vol. octavo j the statical lamp, Edelcrantz, in your 5th 

 volume, together with the gauge to Woulfe's most ingenious 

 apparatus for heating water by waste steam, in your 2nd vol. 

 are among the useful applications of a fluid substituted instead 

 of packing, or leathering, for a moveable piece of the nature of 

 a piston. On the present occasion I send you an application 

 of the same description to a blow pipe which acts upon the 

 principle of the regulating piston in large works. 



The body of the instrument, BB EE, consists of a cylinder, 

 having another interior cylinder, of rather smaller diameter, 

 securely joined to the outer one, at the lower rim of the for- 

 mer, so that both cylinders are concentric, and both open at 

 top j the edge of the inner cylinder being rather the highest. 

 The outer cylinder is set air-tight in the foot E E, and com- 

 municates wjth the lower space D, which has connection with 

 the mouth tube C, and the blow pipe D, by channels which 

 have no other issue. A is a metallic cylinder, closed at the 

 end A, and open at the other, which is the lower end. The 

 letter C denotes a weight connected with the top of A by an 

 inflexible wire or stem. This weight may be changed for one 

 either greater or less, according to the intended force of the 

 blast which is governed by it. The diameter of the cylinder 

 A is such, that it may be inserted mouth downwards in the 

 space between the other two cylinders j and if mercury be 

 th«n poured into that space to about half its depth, the inter- 

 nal 



