AvuGUST 14, 1902] 
Part ili. (M. W. T. and A, J.).—The three small thermo- 
meters used to measure the vapour pressures of liquid oxygen 
were also employed in the case of liquid hydrogen. The small 
bulb, which in the previous experiments had contained pure 
oxygen, now contained pure hydrogen. The agreement between 
the results obtained with different thermometers is indicated 
in the following table :— 
I.—Aydrogen Scale. 
Vapour pressure Temperature. 
Thermometer. of liquid hydrogen. Found. From curve. 
mm. 5 A 
A (12 c.c.) 7572 20°17 20°21 
B (26 c.c.) 766°6 20°28 20°25 
II.— Helium Scale. 
Vapour pressure Temperature. 
Thermometer. of liquid hydrogen. Found. From curve. 
mm. a ° 
A (12 c.c.) 7650 20 42 20°44 
” 759°2 20°41 20°41 
B (26 c.c.) 7700 20°43... 20°46 
Gae7ac:cs) 749'0 20h 20730) 
The vapour pressures were measured between the boiling and 
melting points. The results are as follows :— 
Vapour Pressures of Liquid Hydrogen. 
Pressure in 
Temperature on 
millimetres. 
the helium scale. 
Temperature on the 
hydrogen scale. 
800 20°41 20°60 
760 20°22 20°41 
700 19 93 20°12 
600 19 41 19°61 
500 18°82 19'03 
400 18"15 18°35 
300 17°36 17°57 
200 16°37 16°57 
100 14°93 15°13 
50 — 14°11 
Though the pressure coefficients of hydrogen and helium 
between 0° and 100° C. show no appreciable difference, 
measurements of low temperatures on the scales of the two 
thermometers are not identical. It is probable that at the 
normal temperature both gases may be considered as so nearly 
perfect that the difference between the gas scale and the 
absolute scale is insignificant. As the critical point of helium 
lies much lower than that of hydrogen, measurements of low 
temperatures on the helium scale should approach more closely to 
absolute temperatures than measurements on the hydrogen scale. 
It is pointed out that helium should replace hydrogen as the 
normal thermometric substance. 
The melting point of hydrogen was found to be 14°*10 on the 
helium scale. 
The pure helium used in the thermometric measurements 
was obtained by passing purified cleveite gas through a coil 
cooled to 15° in liquid hydrogen boiling zz vacuo. An unsuc- 
cessful attempt was made to liquefy this gas, which could not 
be condensed at 13° under a pressure of 60 atmospheres. 
The vapour pressures of solid neon were measured at tempera- 
tures corresponding to 20°°4 (12°8 mm.) and 15°°65 (2°4 mm.). 
It was shown that the vapour pressure did not change as 
the solid evaporated, proving that neon is a homogeneous 
substance. 
EDINBURGH. 
Royal Society, July 21.—Prof. Geikie in the chair.—The 
Neill prize for 1898-1901 having been awarded to Dr. J. S. 
Flett for his papers entitled ‘‘ The Old Red Sandstone of the 
Orkneys” and ‘‘ The Trap Dykes of the Orkneys,” Prof. 
Geikie, in making the award, recalled the important work 
which Dr. Flett had done in searching for and finding organic 
remains in rocks hitherto supposed to be unfossiliferous, and 
then in proving that these strata were divisible into definite 
zones, each characterised by its own particular fish fatna. The 
paper on the trap dykes could have been written only by one 
who was at once a skilled field geologist, a thoroughly equipped 
petrologist, an expert microscopist and a facile chemist.—In a 
Yfurther communication on magnetic shielding in «holluw siron 
NO. 1711, VOL. 66] 
NATURE 
83 
| Go 
cylinders and superposed magnetic inductions in iron, Mr. 
James Russell discussed in particular the superposition of two 
magnetising forces at right angles to one another, and the 
magnetic zeolotropy of demagnetised iron. Thus, if H, repre- 
sent the field first acting and H, the field superposed at right 
angles to the first, and if B, and B, represent the resultant 
inductions in the directions of H, and H, respectively, then the 
general result was that with H, superposed on H, the B, com- 
ponent always lay above the B, component. For low fields the 
B, component is greater than in the normal case when no H, 
acts, but as the field is taken stronger the B, component approaches 
the normal value, and finally in high enough fields falls below it. 
The B, component lies below the normal value with this excep- 
tion, that with low values of H, there is a slight excess of the 
B, component over the normal value. Then again, as regards 
xolotropy the following result was established. During the 
early stages of induction, iron is more permeable to a force in 
the same direction as that used in the immediately preceding 
process of demagnetising by reversals than it is to one at right 
angles to it. The results were discussed in terms of the recog- 
nised theories of molecular magnetism.—Dr. W. Peddie, in an 
additional note on the use of quaternions in the theory of 
screws, applied his method of interpretation to the case of a 
rigid body moving with two degrees of freedom, and was led to 
the investigation of the elliptic cylindroid, which differs from 
the ordinary cylindroid by being referred to an elliptic cylinder 
instead of to a right cylinder. Further developments were also 
given.—Prof. C. G. Knott read the second part of a paper 
on change of resistance of nickel due to magnetisation at 
different temperatures. The apparatus was the same as that 
already described, but by a modification in the method of 
experimenting more precise results had been obtained. The 
rate of change of resistance per unit increase of field at con- 
stant temperature and the rate of change per unit increase of 
temperature of this magnetic rate of change in a given field 
being distinguished as the magnetic change rate and the thermal 
variation respectively, the general conclusions were: (1) the 
magnetic change rate of resistance of a given nickel wire 
increases steadily with increase of field, but at a somewhat 
slower rate as the field increases; (2) the magnetic change rate 
increases slightly but unmistakably with rise of temperature up 
to 100° C. and probably higher; (3) the thermal variation of 
this change rate is greater at qo” than at 75° in fields higher 
than about 40, but tends to be less at the lower temperature 
in fields smaller than 35 or 40 C.G.S. units ; (4) the change of 
resistance due to a field applied in a given direction is greater 
when the immediately preceding field has had the same direc- 
tion than when it has had the opposite direction. The results 
were discussed along the lines of Prof. J. J. Thomson’s theory 
of electrified corpuscles.—Prof. Alexander Smith, in continua- 
tion of a previous paper on the freezing point of sulphur, com- 
municated a note on causes which determine the formation of 
amorphous sulphur. The proportion of amorphous sulphur 
formed in a mass of sulphur purified by crystallisation and kept 
heated at 448° C. was found to increase with the time which 
elapsed between the purification and the heating, and to 
decrease as the heating was greatly prolonged. Passing certain 
gases such as air, dry sulphur dioxide and dry hydrogen chloride 
through the sulphur during the heating increased the yield of 
amorphous sulphur ; and under these conditions long continua- 
tion of the treatment did not cause any reduction in the yield. 
On the other hand, nitrogen, carbon dioxide, hydrogen sulphide 
and ammonia, used similarly from the beginning of the heating, 
seemed to prevent the formation of the amorphous form. It 
was not advisable to offer any theory until further work had 
been done. 
PARIS. 
Academy of Sciences, August 4.—M. Bouquet de la 
Grye in the chair.—Reflection and refraction as regards trans- 
parent bodies in rapid motion: reflected and refracted waves : 
amplitude of vibrations, by M. J. Boussinesq.—Experimental 
demonstration of the decomposition of carbon dioxide by leaves 
exposed to light, by MM. P. P. Dehérain and E. Demoussy. 
The authors point out that when the ordinary method of im- 
mersing leaves in a saturated solution of carbon dioxide is 
followed, the results are invariably successful with normally 
submerged aquatic plants like Cevatophyllum submersum, but 
vary greatly with plants the leaves of which normally decompos- 
carbon dioxide in air. The results are satisfactory if the leaves 
30 sv 
