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Art. XVI.—MISCELLANEOUS INTELLIGENCE. 



I. Mechanical Science. 



1. Influence of Temperature on Stone Bridges. — M. Vicat has had 

 occasion to observe a striking instance of the effect of change of 

 temperature on a bridge constructed over the Dordogne at Souillac. 

 The bridge was of stone, had seven arches, each of above twenty-four 

 feet span. It was expected that, as the masonry settled, the parapet 

 stones would separate slightly from each other; and, in fact, this took 

 place, but it occurred suddenly and precisely during the very cold 

 weather of February, 1824. Continuing the observation of what 

 took place at the separation thus formed, it was found that 

 cement, with which portions of the cracks had been filled, remained 

 undisturbed during the cold weather; but that as the warm weather 

 came on, it was pressed out, and the joints were closed : and it was 

 ultimately ascertained, that much of the expansion and contraction 

 of the bridge was entirely thermometrical, depending upon the 

 changes of temperature communicated to it from the atmosphere. 



One of the most important and evident consequences of this action 

 is, that large arches exposed to the variations of natural temperature 

 are never in equilibrium ; and M. Vicat remarks, that these effects 

 are equally produced, and have been observed in arches constructed 

 more than a year previous, and in those which have not been built 

 more than two months ; so that the thermometrical expansion and 

 contraction of the stones does not appear to change by time. — 

 Ann. de Chim. xxvii. 70. 



2. Vibration of Wires in the Air. — A gentleman of Burkil, near 

 Basle, in Switzerland, is said to have observed, some years since, 

 that a long iron wire stretched in the air gave musical tones in cer- 

 tain states of the weather. In consequence of this, and other 

 observations, a kind of musical barometer is described as having 

 been constructed by Captain Hans, of Basle, in 1787. Thirteen pieces 

 of iron wire, each 320 feet long, were extended from his summer- 

 house to the outer court, crossing a garden ; they were placed about 

 two inches apart; the largest were two lines in diameter, the 

 smallest only one, and the others about one and a half. They were 

 on the side of the house, and made an angle of twenty or thirty 

 degrees with the horizon. They were stretched and preserved tight 

 by wheels for the purpose. Durmg certain changes of the weather, 

 these wires make a considerable noise, resembling that of a sim- 

 mering tea-urn, an harmonicon, a distant bell, or an organ. It 

 seems to be supposed, that wires placed east and west yield no 

 sound, and that to produce the effect they must be in the direction of 

 the meridian. In the opinion of M. Dobcrcincr, as stated in the 



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