PHYSICS. 357 



frame. One of the ends of each helix is fixed ; the other acts on a pul- 

 ley so arranged that their mechanical actions are added. The two 

 pallies carry a silk thread attached to a light slide, moving between 

 vertical guides, and carrying a style which presses against a cylinder 

 carrying the paper and moved by clock-work. The hygrometric curve 

 is thus inscribed on the paper. (J. Phys., October, 1886, II, v, 461; C. 

 K., June, 1886, cii, 1371.) 



Luvini has published a series of experiments made by him on the 

 spheroidal state with distilled water, soap- water, alcohol, and ether. 

 He has made the interesting observation that in rarefied air the tem- 

 perature of the spheroidal mass diminishes. On lowering the pressure 

 from 420""" to 50""°, the liquid, always in tlie spheroidal condition and 

 near an incandescent wall, falls in temperature from about 83<^ to near 

 40°; that is, to a temperature at which the maximum elastic force of 

 the vapor is equal to the external pressure. In a closed vessel the tem- 

 perature of the spheroidal liquid rises above the normal temperature of 

 ebullition. It is common in blowing glass to inject a little water into 

 the cavity formed in the hot glass. The liquid becomes spheroidal and 

 its vapor blows out the glass. (II Nuovo Cimento, 1885, xvii, 15 ; J. 

 Phys., December, 1886, II, v, 569.) 



3. Conduction and radiation. — Specific heat. 



Graetz has given the results of his determinations of the conductibil- 

 Ity of liquids for heat, made by his new method, which consists in caus- 

 ing the liquid to flow at a given temperature through a narrow metallic 

 tube whose exterior is maintained at a somewhat lower temperature, 

 and in determining the mean temperature and the volume of the liquid 

 which has passed dliring a given time, when the stationary condition 

 has been established. Assuming that the flow of liquids in narrow 

 tubes may be calculated from Poiseuille's law, the determination of the 

 coefficient of interval conductivity depends on the solution of an equa- 

 tion of partial dift'erences of the second order, which contains no other 

 constants to be determined by experiment than the mean velocity of 

 flow and the radius of the tube. The values obtained were for glycerine 

 0.0382, alcohol 0.0327, ether 0.0227, petroleum 0.0213, turpentine 0.0195, 

 and carbon disulphide 0.0160. The quotient of this coefficient by the 

 product of the density and the specific heat is nearly constant. This 

 coefficient increases slightly with the temperature. (Wied. Ann., xxv, 

 337 ; J. Phys., November, 1886, II, V, 506.) 



The law according to which an incandescent body emits energy has 

 been studied by Moller. A sheet of platinum carried to incandescence 

 by a current, is inclined at an adjustable angle before a Wild photom- 

 eter, a similar plate of i^latinum unaltered in position being used for 

 comparison. Wild's photometer consists of a double prism which brings 

 the beams from the two sources into a common direction, the base of 

 which is covered with ground glass. The emergent and juxtaposed 



