SCIENTIFIC SUMMARY. 
517 
Several distinguished botanists have recently been called from the scene of 
their labours. Carl Ludwig von Blume, M.D., of Leyden, died at that city 
in February ; and another eminent Dutch botanist, Willem Hendrick de 
Yriese, expired at the same place on January 23rd. In our own country, we 
have to lament the death of Mr. Wm. Borrer, F.R.S., a name indissolubly 
connected with the subject of Lichenology. 
CHEMISTRY. 
P URE CHEMISTRY. — Our last quarterly retrospect of Pure Che- 
mistry was introduced by a few facts which had been lately 
discovered respecting the divisibility of matter. More recent researches 
have shown that even the incredible numbers obtained in the former 
experiments fall far short of what we now know must be the actual fact, — 
in the case, at all events, of some volatile liquids. In the course of some 
experiments on the absorption of heat by gaseous matter, Tyndall has 
proved that air, which in its pure state is perfectly transparent to radiant 
heat, becomes absolutely opaque to that force if it contain a minute trace 
of some compound gases and vapours. A layer of ammonia three feet 
long is perfectly black to heat emanating from an obscure source. At a 
tension of one inch of mercury, the absorption of sulphurous acid is 8,000 
times that of air ; and the perfectly transparent vapour of boracic ether, 
at a tension of the tenth of an inch of mercury, has an absorbing power 
upon heat 186,000 times that of air. It is with this latter body that some 
most astonishing results have been obtained with respect to the divisibility 
of matter. By admitting a minute trace of boraeic-ether vapour into the 
experimental tube, exhausting it to the tenth of an inch of pressure by 
means of air-pump, then admitting pure air into the tube and re-exhaust- 
ing it to the same tension, the absorptive properties of the vapour could be 
experimentally observed when only the most infinitesimal fractions of an 
atmosphere were present. By repeated exhaustions and sweeping out of 
the tube by pure air, the professor found that the action upon radiant heat 
of an amount of boracic ether vapour, possessing a tension of only the one 
thousand and twelve million five hundred thousandth (1-1, 012, 500, 000th) of 
an atmosphere was easily measurable. The actual weight of boracic- 
ether vapour present in a cubic inch of air at that tension is so infinitely 
small as utterly to defy the attempts of the human mind to comprehend it. 
Caesium, and Rubidium.— M. Grandeau, whose researches on the two new 
metals discovered by spectrum analysis, Ctesium and Rubidium, were briefly 
noticed in our last number, has continued his investigations, and now finds 
that the latter metal is one of the most widely-distributed bodies in nature, 
being always pr-esent in the mineral constituents of beetroot, tobacco, 
coffee, tea, grapes, and other vegetable substances. These bodies of course 
derive it from the soil, and M. Grandeau gives data by which it is shown 
that the amount annually absorbed from an acre of land by a crop of 
beetroot is somewhat considerable, and by no means to be neglected by 
agricultural chemists in their experimental inquiries into the inorganic 
food of plants. 
Eli Blake, jun., of New Haven, thus explains the discovery of these 
NO. IV. 2 N 
