TRANSACTIONS OP THE SECTIONS. 13 



The lathe was again used as the whirling apparatus, but instead of the ether ther- 

 mometer, we whirled thermo-electric junctions of iron and copper wires. We 

 obtained the following results : — 



1st. The law of the thermal effect was, as with the ether thermometer, proportional 

 to the square of the velocity. 



2nd. The rise of temperature was independent of the thickness of the wire which 

 formed the thermo-electric junction which was whirled. This was decided by experi- 

 ments on wires of various diameters, ranging from y^ to -} of an inch diameter. The 

 rise of temperature was in any of the wires the same as that obtained with the ether 

 thermometer, the bulb of which was nearly half an inch in diameter. 



3rd. The thermal effect appeared likewise to be independent of the shape of the 

 whirled body ; little difference happening in whatever direction the wire was placed. 



4th. The average result was that the wire was warmed 1° by moving at the 

 velocity of 175 feet per second. 



The highest velocity obtained was 372 feet per second, which gave a rise of 5 0, 3, 

 and there was no reason to doubt that the thermal effect would go on continually in- 

 creasing according to the same law with the velocity. Thus at a mile per second the 

 rise of temperature would be 900°, and at 20 miles per second, which may be taken 

 as the velocity with which meteors strike the atmosphere of the earth, 360,000°. 



The temperature due to the stoppage of air at the velocity of 143 feet per second 

 is one degree. Hence we may infer that the rise observed in the experiments was 

 that clue to the stoppage of air, less a small quantity, of which probably the greater 

 part is owing to loss from radiation. It being also clear that the effect is indepen- 

 dent of the density of the air, there remains no doubt whatever as to the real nature 

 of '* shooting stars." These are small bodies which come into the earth's atmo- 

 sphere at velocities of perhaps 20 miles per second. The instant they touch the atmo- 

 sphere their surfaces are immediately heated far beyond the point of fusion, or even of 

 volatilization, and the consequence is that they are speedily and completely burnt 

 down and reduced to impalpable oxides. It is thus that, by the seemingly in- 

 sufficient resistance of the atmosphere, Providence secures us effectually from a 

 bombardment which would in all probability speedily destroy all animated nature, 

 with the exception of the fishes, which would be partly, but not altogether, protected 

 by the water in which they swim. 



The experiments to carry out and verify our previous results on the thermal effects 

 which appear to belong to friction on large surfaces at slow velocities were made as 

 follows : — A disc of zinc or card-board was attached to the revolving axis. An ether 

 thermometer was attached to the disc, the bulb being near the circumference and 

 describing a circle with a radius of about li foot. On rotating the disc at the velocity 

 of If foot per second, as much as one-thirtieth of a degree of heat was developed. 



On the Transmission of Electricity through Water. By J. B. Lindsay. 



The author has been engaged in experimenting on the subject, and in lecturing on 

 it in Dundee, Glasgow, and other places since 1831. He has succeeded in transmit- 

 ting signals across the Tay, and other sheets of water, by the aid of the water alone, 

 as a means of joining the stations. His method is to immerse two large plates con- 

 nected by wires at each side of the sheet of water, and as nearly opposite to each 

 other as possible. The wire on the side from which the message is to be sent is to 

 include the galvanic battery and the commutator or other apparatus for giving the 

 signal. The wire connecting the two plates at the receiving station is to include an 

 induction coil or other apparatus for increasing the intensity and the recording 

 apparatus. The distance between these plates he distinguished by the term "lateral 

 distance." He found that there was always some fractional part of the power from 

 the battery sent across the water. There were four elements on which he found the 

 strength of the transmitted current to depend : first, the battery power; second, the 

 extent of surface of the immersed metal sheets; third, the " lateral distance" of the 

 immersed sheets ; and, fourth, in an inverse proportion the transverse distance or 

 distance through the water. As far as his experiments led him to a conclusion, 

 doubling any one of the former three doubled the distance of transmission. If, then, 

 doubling all would increase the intensity of the transmitted current eightfold, he 

 entered into calculations to show that two stations in Britain, one in Cornwall and 



