298 Chronicles of Science. | April, 
obtained to an examination in this instrument. Within the green 
and on the border of the yellow rays, the well-known characteristic 
dark bands of blood were produced. Only one other substance 
was known to produce similar dark bands—cochineal dissolved in 
ammonia—in which case, however, their position would be different. 
Dr. Herapath said he was satisfied from the evidence this test had 
afforded, that the hatchet had been stained with blood. 
Hzar.—An important paper by Professor Tyndall has lately been 
presented to the Royal Society. It is divided into ten sections. In 
the first, the experiments of Sir William Herschel and of Professor 
Miller, on the sun’s radiation, are described. In the second are 
given a series of measurements, which show the distribution of heat 
in the spectrum of the electric light. In the third section is 
described a mode of filtering the composite radiation of an intensely 
luminous source, so as to detach the luminous from the non-luminous 
portion of the emission. The ratio of the visible to the invisible 
radiation determined in this way is compared and found coincident 
with the results of prismatic analysis. The eminent fitness of a 
combination of iodine and bisulphide of carbon as a ray-filter is 
illustrated. In the fourth section, experiments with other sub- 
stances are described ; various effects obtained im the earlier experi- 
ments on the invisible rays bemg mentioned. In the fifth section, 
the absolutely invisible character of the radiation is established ; it 
is also proved that no extra-violet rays are to be found at the 
obscure focus. Numerous experiments on combustion are also 
described in the fifth section. The sixth section deals with the 
subject of calorescence, or the conversion of obscure radiant heat 
into light. In section seven, various modes of experimenting are 
described, by which the danger incident to the use of so inflammable 
a body as the bisulphide of carbon may be avoided. In the eighth 
section are described experiments on the invisible radiation of the 
lime-light and of the sun. In the ninth section, the effect obtained 
by exposing papers of different colours at the dark focus are men- 
tioned ; while the tenth and concluding section deals with the 
calorescence obtainable from rays transmitted by glasses of various 
kinds. 
In a subsequent paper on radiation and absorption, Professor 
Tyndall considers the department of certam additional elementary 
bodies towards radiant heat. He exposes powders and liquids of the 
same physical character, but differmg from each other chemically, 
at a focus of dark rays, and describes the different effects produced. 
He examines and explains the experiments of Franklin on the 
absorption of solar heat. He then determines the radiating power 
of a great number of substances in the state of fine powder, and 
finds, contrary to the current belief, that in this state also chemical 
