MUSICAL BAROMETER. 265 



the absurdity of the supposition of nature's abhorrence of a vacuum exten- 

 ding to the height of 32 feet, and the true cause was soon observed. The 

 atmospheric pressure acting upon the mercury contained in the cistern, 

 while the surface of the mercury contained within the tube was protected 

 from that pressure, supported the weight of that column ; and by the 

 principles of hydrostatics, we know that the height of the column of mer- 

 cury will be the same whatever be the bore of the tube ; and it stands to 

 reason, that as the atmospheric pressure varies, so will the weight which 

 that pressure supports. The rising and falling, therefore, of the column of 

 mercury within the tube will indicate the atmospheric pressure. We 

 therefore now have a barometer, a term derived from two Greek words, 

 signifying baros, weight, and metron, measure. 



A column of mercury the height of the barometer, and whose base is a 

 square inch, will weigh about I51bs. avoirdupois ; therefore when the 

 barometer stands at 30 inches, the atmosphere exerts a pressure equiva- 

 lent to lolbs. on every square inch of mercury in the cistern; taking, 

 therefore, the barometric column at thirty inches, it follows that all 

 bodies at the surface of the earth sustain a pressure of 15 Ibs. on every 

 square inch of surface ; and, consequently, if the body of a man contains 

 1500 square inches, he sustains the enormous pressure of 22, 500 pounds. 



MUSICAL BAROMETER. 



A GENTLEMAN at Burkli, by the name of Ventain, not far from Basle, 

 in Switzerland, invented, soma years ago, a sort of musical barometer, 

 which has beea called in German, vcetter harfe, weather harp ; or riesen 

 Jiarfe, giant harp, which possesses the singular property of indicating 

 changes of the weather by musical tones. This gentleman was in the 

 habit of amusing himself by shooting at a mark from his window, and 

 that he might not be obliged to go after the mark at every shot, he fixed 

 a piece of iron wire to it, so as to be able to draw it to him at pleasure. 

 He frequently remarked that this wire gave musical tones, sounding 

 exactly an octave, and he found that any iron wire, extended in a direc- 

 tion parallel to the meridian, gave this tone every time the weather 

 changed. A piece of brass wire gave no sound, nor did an iron wire 

 extended east and west. In consequence of these observations a musical 

 barometer was constructed. In the year 1787, Captain Haas, of Basle, 

 made one in the following manner; thirteen peices of iron wire, each 320 

 feet long, were extended from his summer house to the outer court, 

 crossing a garden. They wer> laced about two inches apart ; the 



