1872.] Heat. 27% 
by Mr. W. Carruthers, F.R.S, it was mentioned that the late W. Nicol 
of Edinburgh, well known as the inventor of the single image prism, was the 
discoverer of the mode now in use of making sections of fossils for microsco- 
pical examination. His large collection is now deposited in the British Museum. 
A good substitute for a cement which is a favourite with many microscopists, 
although far from trustworthy, viz. asphalte, will be found in a varnish 
employed by Messrs. Horne and Thornthwaite in the process of etching ther- 
mometer tubes and other glass instruments. Ordinary varnishes were found 
to fail for this purpose, as they permitted the hydrofluoric acid to creep under 
the ground and so cause a rough imperfect line to be etched; the new varnish 
resists the acid perfectly. Its good qualities for the microscopist are—that it 
adheres well to glass, and when hard does not become brittle, but comes 
away in shreds when scraped, like gold size, the most reliable of varnishes 
for fluid mounting ; its advantage over gold size is that it possesses more body, 
owing to an admixture of a suitable quantity of copal. This property renders it 
very suitable for making cells on the turntable; these are, however, much 
improved by baking at a moderate temperature, like japanned wares, without 
which process all cells formed of oil varnish are liable to be softened by sub- 
sequent coatings: neglect of this precaution is a frequent cause of objets 
mounted in such cells being spoiled by the running in of the cement. 
HEAT. 
M. Laborde has made some experiments on calefaction. He let a thin 
thread of water pass through the jet from the blowpipe, and he found on 
examination that the water which had thus passed through a heat capable of 
melting almost any metal was but slightly warmed; in fac, the difference 
was but 3°. Ifa jet is passed through an ordinary flame the increase in 
temperature is considerably higher, probably owing to the incandescent 
particles carried away by the liquid from the smoke. A sheet of water 
presents similar evidence. If the jet from the blowpipe is directed against it 
it is not pierced, nor is there any sensible heating effe&; the finger can be 
brought to within a few millimetres of the flame, and yet there is no sensatiom 
to indicate the near proximity of an otherwise so potent source of heat. 
“The event of the séance,” says the Abbé Moigno, in ‘‘ Les Mondes,” 
speaking of a recent meeting of the Academy of Sciences at Paris, ‘‘ was a 
truly singular and noteworthy incident connected with the subject of the sun’s 
temperature. On the one hand, Father Secchi maintained, and attempted 
to establish, his figure of ten million degrees of temperature (centigrade) 
against MM. Ericsson, Zéllner, and Faye; on the other hand, M. Vaulle, 
Professor of the School of Mines, and formerly a Laplace prizeman, estab- 
lished by means of a very learned and novel theory, a maximum temperature 
of 10,000 degrees. Thereupon, M. Henry Sainte-Claire Deville announced 
that he is engaged in determining the temperature and pressure at the sun’s 
surface, and asserted (as the result of his first researches) that the sun’s tem- 
perature exceeds some three or four times the temperature at which platinum 
melts, amounting, therefore, to from 6000 to 8000 degrees. Next, M. Fizeau 
stated, that having compared (like M. Leon Foucault) the solar light with that 
of the glowing carbon points of the electric light, he had estimated that the 
former is about three times as intense as the latter; hence, inferring the 
relative calorific intensities from the observed relative luminosities, he also had 
deduced a solar temperature of 8000 degrees. So that, according to French 
science, the solar heat does not exceed 10,000 degrees; and, in fad, it is 
emitted by ignited and dissociated terrestrial elements. 
MM. E. and M. Becquerel have made some observations on the differences 
of temperature at divers depths between turfed and denuded soil, when both 
were covered with snow. They were made in the Jardin des Plantes, Paris, 
two contiguous pieces of ground being chosen for the purpose, one of which 
was covered with short vegetation, the other being bare. The thermo-eledric 
pile was used to detect the differences of temperature. Snow commenced to 
fall at Paris about two o’clock in the afternoon on the 7th of last December ; 
