Frsruary 18, 1897 | 
IAT URE 
381 
readily in air when hot than whencold. The difference between 
a positive and a negative charge is also more strongly marked 
at high temperatures, the negative charge being more rapidly 
dissipated.— Point discharge potentials in air and hydrogen, by | 
K. Wesendonck. The quantity of negative electricity dis- 
charged into hydrogen is greater than the quantity of positive 
electricity discharged at the same potential, but the initial | 
discharge potentials are not necessarly different.—The atomic | 
theory in natural science, by L. Boltzmann. The conception of 
the atom cannot be finally superseded by the differential 
equation as applied to a cont/nwum, since the latter is itself | 
based ultimately upon the conception of a discrete structure, 
even in such applications as Fourier’s theory of thermal conduc- | 
tivity. The atom has also the advantage of greater immediate 
clearness and picturesqueness over the differential equation, | 
whether it really exists or not.—On discharge rays, and their 
relation to kathode and Rontgen rays, by M. W. Hoffmann. | 
Discharge rays are contained in the spark discharge in air, | have been made on window glass and ice. 
hydrogen, and nitrogen at ordinary or low pressures. They 
exert no photographic action, but may be discovered by their 
property of imparting luminescence to solid solutions of man- 
ganese sulphate in gypsum when heated to a temperature below 
incandescence (thermo-luminescence). They are intercepted by 
mica, quartz, fluorspar, and other solids, unless produced at low 
pressures. They proceed in straight lines, and are not deflected 
by a magnet. They differ from ultra-violet light in their power 
of penetrating air, and not fluorspar. They are not reflected by 
solids. —Platinised electrodes and determinations of resistance, | 
by F. Kohlrausch. The solution used by Lummer and 
Kurlbaum for making bolometers, viz. one part platinum 
chloride, to 0’008 lead acetate and 30 water, gives a platinum 
black, which is very useful for platinising electrodes. It facilitates 
the use of smaller electrodes for alternate-current resistance 
measurements, and gives a well-marked minimum of telephone 
effect.—Electric moment of tourmaline, by W. Voigt. This 
was determined by breaking the tourmaline into fragments, and 
was found to be 3374 C.G.S. units. —A new formula for spec- 
trum waves, by J. J. Balmer. The author substitutes for the 
infinite geometrical progression in Kayser and Runge’s formula 
a closed term, and gives the frequencies for the lines of each 
series in the form A—B/(z + c)*. 
SOCIETIES AND ACADEMIES. 
LONDON. 
Royal Society, January 21.—‘‘On Reciprocal Innervation 
of Antagonistic Muscles.” Third Note. By C.S. Sherrington, 
F.R.S., Holt Professor of Physiology, University College, 
Liverpool. Received December 29, 1896. 
If transection of the neural axis be carried out at the 
level of the crura cerebri in, e.g. the cat, there ensues after a 
somewhat variable interval of time a tonic rigidity in certain 
groups of skeletal muscles, especially in those of the dorsal 
aspect of the neck and tail and of the extensor surfaces of the 
limbs. The details of this condition, although of some 
interest, it is unnecessary to describe here and now, except in 
so far as the extensors of the elbow and the knee are concerned. 
These latter affect the present subject. The extensors of the 
elbow and the knee are generally in strong contraction, but 
altogether without tremor and with no marked relaxations or 
exacerbations. On taking hold of the limbs and attempting to 
forcibly flex the elbow or knee a very considerable degree in- 
deed of resistance is experienced, the triceps brachii and quad- 
riceps extensor cruris become under the stretch which the more 
or less effectual flexion puts upon them, still tenser than before, 
and on releasing the limb the joints spring back forthwith to 
their previous attitude of full extension. Despite, however, 
this powerful extensor rigidity, flexion of the elbow may be at 
once obtained with perfect facility by simply stimulating the 
toes or pad of the fore foot. When this is done the triceps 
- enters into relaxation and the biceps passes into contraction. 
If, when the reflex is evolved, the condition of the triceps 
muscle is carefully examined, its contraction is found to under- 
go inhibition, and its tenseness to be broken down synchronously 
with and indeed very often accurately at the very moment of 
onset of reflex contraction in the opponent prebrachial muscles. 
The reaction can be initiated in more ways than one, electrical 
excitation of a digital nerve or mechanical excitation of the 
NO. 1425, VOL. 55 | 
| periods such as 1/10° second, its value is less than 
| and Minerals.” 
sensory root of any of the upper cervical nerves may be em- 
ployed; I have seen on one occasion a rubbing of the skin of 
the cheek of the same side effective. 
Similarly in the case of the hind limb. The extensor muscles 
of the knee exhibit strong steady non-tremulent contraction 
under the appropriate conditions of experiment. The applica- 
tion of hot water to the hind foot then elicits, nevertheless, an 
immediate flexion at knee and hip, during which not only are 
the flexors of those joints thrown into contraction, but the 
extensors of the knee joint are simultaneously ve/axed. Electric 
excitation of a digital nerve or of the internal saphenous nerve 
anywhere along its course will also initiate the reflex. 
January 28.—‘‘On the Capacity and Residual Charge 
of Dielectrics as affected by Temperature and Time.” By J. 
Hopkinson, F.R S., and E. Wilson. Received December 15, 
1896. 
The major portion of the experiments described in this paper 
It is shown that for 
long times residual charge diminishes with rise of temperature in 
the case of glass, but for short times it increases both for glass and 
ice. The capacity of glass when measured for ordinary durations 
of time, such as 1/1ooth to r/roth second, increases much with rise 
of temperature, but when measured for short periods, such as 1/10° 
second, it does not sensibly increase. The difference is shown 
to be due to the residual charge which comes out between 
1/50,000th second and 1/1ooth second. The capacity of ice 
when measured for periods of 1/100th to 1/1oth second 
increases both with rise of temperature and with increase of 
time ; its value is of the order of 80, but when measured for 
Sone: 
difference again is due to residual charge coming out during 
short times. In the case of glass, conductivity has been: 
observed at fairly high temperatures and after short times 
of electrification; it is found that the conductivity after 
1/50,000tk second electrification is much greater than after 
1/T0,000th, but for longer times is sensibly constant. Thus a 
continuity is shown between the conduction in dielectrics which 
exhibit residual charge and deviation from Maxwell’s law and 
ordinary electrolytes. 
February 4.—‘‘ On the Gases enclosed in Crystalline Rocks 
By Prof. W. A. Tilden, F.R.S. 
From the time of Sir Humphry Davy it has been known that 
many minerals contain gases as well as liquids enclosed in. 
| cavities, which are often large enough to be visible to the unaided 
eye. The liquid sometimes consists of water or saline solutions, 
occasionally of mineral naphtha, and not unfrequently of carbon 
dioxide, which is recognisable by its great expansibility and total * 
disappearance when the temperature is raised to about 31° C. 
The presence of gases other than nitrogen and carbon dioxide 
in natural crystals had not been observed, save in one or two 
isolated cases, until two years ago, when helium was discovered 
in certain minerals by Ramsay. 
In the course of experiments undertaken with the object of 
ascertaining, if possible, the condition in which this element, 
remarkable for its chemical inactivity, is contained in these 
minerals, I was led to the observation that granite when heated 
in a vacuum gives off several times its volume of gas, which is - 
combustible, and which consists largely of hydrogen and_car- 
bonic oxide. I now find that these two gases are contained, 
more or less abundantly, in all the crystalline rocks, and, to-- 
gether with carbon dioxide and small quantities of nitrogen and. 
marsh gas, are apparently enclosed in fine cavities which per~ 
meate the crystals of quartz, felspar, and other mineral con- 
stituents. ; 
Of twenty different rocks examined—granite, gneiss, gabbro, 
schist, or basalt of different geological ages and from widely 
different localities—all yielded gas in which hydrogen is present, 
and is usually the preponderant ingredient of the mixture. The 
total bulk of the gases extracted, varied from a volume equal to 
1°3 times the volume of the rock to 17°8 times its volume. Lava 
also gave gas, though in smaller quantity, and this also contained 
hydrogen. Graphite, quartz, beryl and tinstone, as examples 
of definite minerals associated with the older rocks, gave a similar 
result. ; 
To account for the large proportion of hydrogen and carbonic 
oxide in these gases, we must suppose that the rock enclosing 
them was crystallised in an atmosphere rich in carbon dioxide 
and steam, at the same time in contact with some easily oxidis- 
able substance, probably a metal or metallic carbide, at a mode- 
rately high temperature. No free oxygen has been found in any 
