Blasting of Rocks. — Velocity of Sound. — French Chrojiometer.73 



BLASTING OF ROCKS. 



Colonel Warnaghen, of the Brazils, has made an important 

 discovery; he has ascertained that the sawdust of wood, espe- 

 cially of woods of the less harder sort, triples the force of the 

 powder employed in hlowing up rocks when mixed with it in 

 equal parts. 



VELOCITY OF SOUND. 



It appears from experiments lately performed at San Jago, in 

 Chili, by M. D. Josef de Epinosa and D. Felipe Bauza, that 

 sound moves with a velocity of 1,227 English feet in a second, 

 the air being at a temperature of 73*5 Fahr. and the barometer 

 27'44 inches. 



FRENCH CHRONOMETER. 



This chronometer consists of a needle perforated tow^ards the 

 middle by an axis fixed in the centre of a vertical dial-plate, and 

 which turning freely around that axis has the property of indi- 

 cating the hour upon the dial-plate. 



It is not directed by any external moving power, and contains 

 in itself all the principle of its action. 



It completes in twelve hours its revolution around a dial-plate, 

 whose divisions, not equal but proportional, are passed over in 

 equal times, as those of a solar dial are by the shade. 



It has no other point of support tlian the immoveable axis 

 round which it turns ; its extremities are insulaied, and have no 

 communication with the centre. 



If the needle is directed towards another hour than that which 

 it indicates on the dial-plate, it returns of itself, like the needle 

 of a compass when attempted to be diverted from its polarity, 

 and after an extremely free oscillation recovers its first position ; 

 so that it can never stop or rest in apparent repose, but at that 

 point of the circumference which corresponds with the time of 

 day. 



if the needle is separated from its axis and removed from the 

 dial-plate, although to a situation where it is kept immoveable, 

 it does not lose any of its anterior properties ; that is to say, on 

 being replaced on the axis, it does not stop at the hour at which 

 it pointed when last removed from the dial-plate, but seeks out 

 and rests at the time of day when it is replaced. 



It preserves for fifteen days all these properties ; and they are 

 renewed by a very simple operation. 



It may be varied in its form and its dimensions. The speci- 

 men which is seen at Feschot's, the watchmaker, No. 18, Rue 

 des Filles St. Thomas, one of the inventors, indicates the hour 

 upon a dial-plate of thirty inches in diameter ; it is in crystal, 

 and the point which directs itself upon the hour is a gilded fleur 

 de lis. 



The 



