466 Scientific Intelligence, 
snow were employed. A first series of experiments, less oir: 
were carried out, with the difference of pressure varia a sec- 
ond, consi erably more exact, with the difference prea og The 
results of the two series agree very well, and confirm those of 
Mayer’s experiments in a shai: satisfactory manner. For the 
co-efficient of friction jc at the temperature ¢ there were found : 
According to the first series, s¢ = -0001706 (1+4-002735 ¢). 
According to the second series, 44 = ‘00016477 (1-+-"002723 ¢). 
—Roy. Acad. of Vienna, Feb. 4th, 1875; Phil. Mag., ae $32, 
P. 
9. Specific Heat of Carbon, Boron and Silicon. he TL F. 
WeEsER presented a paper on ‘this subject at the fift ‘sixth anni- 
versary of the Royal Witirtemberg Land and Forest Management 
Academy at Hohenheim. ‘The law of Dulong and Petit, that the 
product of the specific heat by ahi § atomic weight i is constant, holds 
true for most of the solid elements. Carbon, boron and silicon, 
however, seem to deviate considerably from this law, and give dif- 
ferent ae ph in their various allotropic Spit, comparison 
the ts of different observers shows that while they differ 
very pies ey from one another, the larger the interval of tempera- 
ture e co se hte the greater the result. 
Dr. ber has accordingly made a series of Sr ae at 
temperatures from — 80° to 1,000°. The amount of heat was 
determined by Bunsen’s ice cal orimeter, vig the seiiparattiss 
when below 300° by a thermometer ; f er temperatures the 
~The firs ¢ erpetiinened were on the specific heat of the diamond. 
The collections of the Universities of Berlin and Vienna were 
graphite, and leads to the following cman sions :—That from a 
red heat upward, the specific heat of carbon does not vary more 
than the specific. heats of those element which fulfil the law of 
that of the diamond modification of carbon. malies, 
therefore, disappear above 600° C.,and carbon then obeys the 
abo parison of the specific heats of graphite, of 
PA oon 
dense amorphous carbon and of porous carbon showed that they 
were identical within the temperature interval 0° to 225°. A unit 
weight of porous carbon, as far as possible free from water, evolves 
4°16 heat-units when wetted with water 
In the case of boron two hundred small crystals were used, hav- 
ing a total weight of 67 grams. The observations were extended 
from —40° to + 230° A showed a similar increase to that of 
carbon. It is, therefore, very probable that at higher Sl a 
tures the specific heat attains a constant value of ‘about “50, and 
consequently the number 11, which is generally sisitat ‘a the 
