158 ANNUAL OF SCIENTIFIC DISCOVKKY 



V 



lie calls observation to the fact that one who gives his close 

 attention to both the wires and soumls will liml that the latter 

 make their appearance likewise when there is a total absence of 

 wind, and in a quirt mornini^ 'n winter, when the wires appear 

 covered with trost to the thiekness ot a Ihi^X'^^r, they nevertheless 

 carried on lively vibrations and s\vin«;in;2; while the air was totally 

 qniet. The observer had noticed this for 18 years past, and at 

 last was led to the real cause of the phenomenon. 



According to him, therefore, the vibrations arc due, not to the 

 wind, but the changes of atmospheric temperature, and especially 

 through the action of cold, as lowering of the temperature in- 

 duces a shortening of the wires, extending over the whole length 

 of the conductor. A considerable amount of friction is produced 

 on the supporting bells, and this gives the explanation for the 

 sounding both in the wires anil the poles. This explanation also 

 concurs with the fact that poles bearing but one or a few wires 

 give olf far louder sounds than when loaded with many, because 

 in the latter case the vibrations produced must be less uniform 

 and simultaneous. 



EXPERIMENTS WITH THE GREAT INDUCTION COIL AT THE 



ROYAL rOLYTECHNIC. 



We extract from the *' Chemical News" the following abstract 

 of a paper communicated to the Royal Society, by J. P. Gassiot, 

 F.ll.S. : — 



" The length of the coil from end to end is 9 feet 10 inches, and 

 the diameter 2 feet; the whole is cased in ebonite; it stands on 

 two strong pillars covered with ebonite, the feet of the pillars 

 being of a diameter of 22 inches. The el)onite tubes, etc., are the 

 largest ever constructed by the Silver Town Works. 



"The total weight of tlie great coil is 15 cwt., that of the ebo- 

 nite alone being 477 lbs, 



"The primary wire is made of copper of the highest conductiv- 

 ity, and weighs 145 lbs. ; the diameter of this wire is 0.0925 of an 

 inch, and the length 3,770 yards. The number of revolutions of 

 the jnimary wire rouml the core of soft iron is G,000, its arrange- 

 ment being 3, G, and 12 strands. 



*' The total resistance of the primary is 2.201400 British Associ- 

 ation units, and the resistance of the primaiy conductors are re- 

 spectively, for three strands, 0.733800 British Association units ; 

 six, b.3GG945 B.A. units; twelve, 0.1834725 B.A. units. 



"The primary core consists of extremely soft straight iron 

 wires 5 feet in length, and each wire is O.OG25 of an inch in diam- 

 eter. The diameter of the combined wires is 4 inches, and the 

 weight of the core is 123 lbs. 



" The sccondaiy wire is 150 miles in length ; it is covered with 

 silk throughout, and the average diameter is 0.015 of an inch. 



" The total weight of this wire is GOG lbs., and the resistance is 

 33.5G0 B.A. units. The length of the secondary coil is 55 inches, 

 and the insulation throughout is calculated to be 95 per cent, be- 



