112 On the Horary Oscillations of the Barometer at Rome. 



A hole was bored about twenty-six inches deep and one and a- 

 half inch diameter in a large block of greenstone. It was 

 tried to blast this rock with powder and loose sand, and the 

 latter was blown out. The same charge of powde)- was then 

 put in, and the mouth of the hole closed with a wooden plug 

 about five inches long, with a touch hole bored through it, and 

 driven into the aperture with a mallet. Between the powder 

 and the lower part of the plug an interval of several inches was 

 left, and the communication was perfected by means of a tin 

 tubule filled with powder, and passed through the centre of the 

 plug. On firing it the rock was rent in every direction to the 

 distance of four feet, and several large pieces were detached, 

 one of them weighing fully a ton. The advantages are, that 

 the plug is as safe and more efficacious than the sand, and 

 that with it the force if it goes out may easily be replaced, 

 whereas with sand it becomes necessary to have recourse to 

 the tedious operation of again scooping out the contents of the 

 hole as far down as the charge of powder. The only time I 

 succeeded with sand was when the hole was bored near the ex- 

 terior edge of the rock, and then a slice was cut off. It may 

 be proper to mention that the sand used was the ordinary 

 kind procurable from the river banks, and rather fine-grained. 

 I think it is probable that the method above explained would 

 be applicable to bursting or rendering cannon unserviceable. 

 The great effect produced is, I conceive, chiefly owing to the 

 interval left between the charge of powder and the plug, as it 

 is well known to sportsmen that a gun will certainly burst as 

 the barrel opens, if a ball or charge of shot be not properly 

 rammed down. 



Art. 'SJL.'^Memoir on the Horary Oscillations of the Ba- 

 rometer at Rome. Communicated by the Author. 



Amongst the various branches of the science of meteorology 

 few have been so little investigated as the horary variations of 

 the barometer ; and indeed till lately so little has it been at- 

 tended to, that in few meteorological essays or treatises which 

 I have seen has it been noticed, and in still fewer has it elicit- 

 ed facts or discmsions proportioned to its interest and singu- 



