114 PHILOSOPHICAL TRANSACTIONS. [anNO 1684-5. 



a rag, and put into it about 2 or 3 oz. of powder, over which they put a thin 

 paper, and on it place the gun, which they bind firmly into the hole, by driving 

 in against the flat side of the upper part of it, the third instrument, which is 

 a little iron wedge, 4 inches in length, by the miners called a quionet, fig. 13; 

 when this is done they pass down a wire through the hole drilled in the gun, 

 and pierce the paper which covers the powder ; then they prime the gun, and 

 lay a train, retiring up out of the work before the powder takes fire. The paper 

 is put at first over the powder, lest when the gun and quionet are driven down, 

 the tools should strike fire and kindle the powder. 



These instruments will be of great use to miners ; for, besides what will be 

 saved in timber in a year that is used in burning rocks, which is very consi- 

 derable, we know that as soon as a man has fired his powder and split the rock, 

 he may presently go to work again ; whereas after a fire is laid in a shaft, a man 

 can scarcely go to work in 24 hours after, the rocks being too hot to suffer 

 him. 



On the Advantages of High Wheels. By a Member of the Philosophical Society 



of Oxford. N" 167, p. 856. 



Having read in the mechanics of Mersenne, Herigon, and Dr. Wallis, that 

 the larger the wheels of a coach, &c. are, caeteris paribus, the more easily 

 they may be drawn over a stone or such like obstacle ; I was willing to try some 

 experiments which I thought might convince some men better of the truth of 

 it than a mathematical demonstration. 



I therefore ordered a model of a part of a waggon to be made, consisting of 

 4 wheels, 1 axles, and a board nailed upon these. The smaller wheels were 4-j- 

 inches high, and the larger wheels 5f, viz. -^ of the ordinary height of the 

 wheels of a waggon, the weight of the model was almost a pound and half. I 

 had also 1 other wheels made 5f inches high, to be put on instead of the 

 smaller. The middles of the 1 axles were Q\- inches asunder. All the wheels 

 turned very easily on the axles. 



A piece of lead 50|- lb. avoirdupois was laid upon the model, so forward that 

 the smaller wheels seemed to bear above •§- parts of the weight. Then the mo- 

 del was drawn with a string laid over a pulley, the top of which was ^ of an 

 inch higher than the top of the hinder axles, and the middle of this pulley was 

 74. inches from the middle of the fore axle. The lesser wheels being put on, 

 and the string fixed, tied to the top of their axle : then 



1 . 3 lb. drew the model on the smooth level table. 1. 20 lb. drew the lesser 

 wheels over a squared rod + of an inch thick. 3. 30 lb. drew them over a round 



