608 SCIENTIFIC RECORD FOR 1885. 



pressure on a square mile would be about 1 pound, and whose specific 

 heat is such that it would require as much heat to raise the temperature 

 of 1 pound of it 1° F. as it would to raise about 2,300,000,000 tons of 

 water the same amount, will satisfy the requirements of nature in being 

 able to transmit a wave of light or heat 186,300 miles per second and 

 transmit 133 foot-pounds of heat energy from the sun to the earth each 

 second per square foot of surface normally exposed, and also be every- 

 where practically non-resisting and sensibly uniform in temperature, 

 density, and elasticity. This medium we call the luminiferous aether." 

 {Phil. Mag., November, 1885, V, xx, 389.) 



Fitzgerald has described some mechanical models to illustrate certain 

 properties of the aether. The elements consist of pairs of wheels so 

 geared together that when one rotates it causes the other to rotate in 

 the same direction. For a one-dimensional model a baud suffices to con- 

 nect them. By fixing a number of wheels with their axes parallel and 

 at right angles to a plane and connecting each wheel with its neighbors 

 by elastic bands we shall have such a model which represents a non- 

 conducting region of the ether. A perfectly conducting region is one 

 in which there are no bands, and a partially conducting region would 

 be represented by the bands slipping more or less. By means of such 

 a model the author discusses electrostatic, electrokinetic, and luminif- 

 erous phenomena, preliminary to a description of the tridimensional 

 model, which is the object of his paper. {Phil. Mag., June, 1885, V, 

 XIX, 438.) 



Trowbridge has experimented to produce, by means of an electric cur- 

 rent, a standard of light which shall be always the same under the same 

 conditions. His first experiments were made with platinum, a strip of 

 foil 5''™ long, 5™™ wide, and 0-02'"'" thick being placed in the shunt cir- 

 cuit of a small Gramme machine, and inclosed in a Ritchie photometer 

 box for comparison with a standard candle, the current being measured 

 with a tangent galvanometer, and the difference of potential at the ends 

 of the strip with a quadrant electrometer. With a variation of electro- 

 motive force of 2-6 to 3*8 volts and of resistance from 0*44 to 0-47 ohm, 

 the current varied from 6 to 8 amperes, and the light from a very dull 

 red up to the color of a candle. Next a thermal junction was inclosed 

 in an Edison incandescent lamp to see if the heat radiation was pro-, 

 portional to the incandescence, but the thermo-electric force developed 

 was too feeble. A. loop of fine platinum wire was then inserted between 

 the terminals of the carbon in an Edison lamp and made one side of a 

 Wheatstone bridge, a similar wire forming a second side, thus constitut- 

 ing a bolometer. With an increase of resistance of the inside loop of 

 0*2 ohm, there was an increase of light from 3 to 7*5 candles. Though 

 sensitive, this arrangement does not enable rays of different refrangi- 

 bility to be distinguished. Experiments were then made to determine 

 the practicability of using a thermopile to measure the amount of ra- 

 diation from an incandescent strip of platinum at a fixed distance, and 



