518 
NATURE [JULY 8, 1915 

I recorded 3°12 in. of rain between 8.30 p.m. and 
10 p-m., due to the thunderstorm. There can be no 
doubt about the time and quantity, as I had the rain- 
gauge checked by tanks and trucks which stood close 
bya 
A SCIENTIFIC paper recently issued by the Bureau of 
Standards deals with the emissivities of metals and 
oxides at temperatures near their melting points. The 
work is by Messrs. G. K. Burgess and R. G. Walten- 
berg, who use throughout the micropyrometer in- 
vented by the former three years ago. A speck of the 
substance weighing about a hundredth of a milligram 
is placed on a platinum strip which can be heated in 
an atmosphere of air, hydrogen, or other gas until 
the substance melts. On cooling it presents a smooth, 
clean surface. The carbon or tungsten filament of 
the micropyrometer is then brought alternately to the 
same brightness as the bare and as the covered 
platinum when viewed through coloured glasses. The 
emissivity of platinum being known for all the tem- 
peratures used, the temperatures and emissivities of 
the substances can be calculated. For the wave- 
lengths at which the comparisons are made the metals 
do not appear to change their emissivities much in the 
20° C. below their melting points, but some of them 
and some of their oxides show a marked increase of 
emissivity on melting. This increase of emissivity on 
melting in the case of platinum makes the Violle unit 
of light uncertain. 
Tue Economic Proceedings of the Royal Dublin 
Society (vol. ii., No. 10, p. 161) contains an account 
by Prof. G. T. Morgan and Mr. G. E. Scharff of 
preliminary experiments on the utilisation of peat tar. 
The tar produced by distilling peat in retorts, producer 
gas plants, or other suitable distilling apparatus, yields 
certain neutral oils which differ from the aromatic 
oils of coal tar and from the paraffins in having a- 
highly unsaturated character manifested by the rapid 
absorption of atmospheric oxygen. The alkaline ex- 
traction of these oils leads to the separation of acidic 
oils of high boiling point and of great germicidal 
power. The higher fractions of the neutral oils yield 
waxes resembling the Montana wax of lignite. The 
crude peat tar oil contains small amounts of basic 
substances of the pyridine group, whilst the residue 
of the distillation is a typical soft pitch. 
AN interesting paper on a greatly improved haemin 
test for blood is published by Dr. William Beam and 
Mr. Gilbert A. Freak in the Biochemical Journal 
(vol ix., p. 161). The difficulties experienced with 
Teichmann’s test when applied to stains, both fresh 
and old, are due chiefly to the too rapid evaporation 
of the solvent, and, to a less extent, to interference 
of the albuminous matter of the blood with the crystal- 
lisation. Evaporation should be extremely slow, and 
when carried out in the manner detailed in the original 
paper, which also eliminates the harmful effect of 
albumin, crystals are obtained with the greatest cer- 
tainty and of remarkably large size, even though 
only a minute amount of blood be present. The test 
as described was found to be equally applicable to 
bloodstains, fresh or even twelve years old, stains 
NO. 2384, VOL. 95] 

partially removed by soap and water or heated to 
110°, or mixed with earth, or to old stains on rusty 
iron which had been exposed to strong sunlight and 
atmospheric conditions during several days. Of the 
reagents which have been recommended for Teich- 
mann’s test, acetic acid is by far the best. It suffices 
for the test with bloodstains which have not been 
extracted with water, but as a precautionary measure 
it is best to use a reagent containing a minute pro- 
portion—about o-or per cent.—of sodium chloride. 
Tue Journal of the Society of Chemical Industry 
(vol. xxxiv., No. 10, May 31) contains an account by 
Dr. E. Howard Tripp of a novel system of sewage 
treatment, called the Dickson centrifuge process. The 
Dickson method of separating the solids from sludge 
consists in treating it with o-5 per cent. of yeast for 
twenty-four hours at 33° C. Owing to the escape of 
gases set free by anaerobic fermentation, the solids 
rise to the surface, from which they are run off; in 
this manner fully half the water-content of the sludge 
is eliminated. Live brewer’s yeast is the most effec- 
tive agent, but dextrose, starch, and other substances 
which act as nutrients to the bacteria, produce the 
same result. The separated sludge is then completely 
dried by exposure to hot air in a plant which resembles 
that used in France for drying pulverised coal-dust. 
The dried material contains 3 per cent. of nitrogen 
and 50 per cent. of organic matter, and has proved 
itself to be a valuable fertiliser, either alone or as a 
base for artificials. The centrifuge treatment of 
effluents of all kinds consists in passing them through 
a centrifugal machine the perimeter of which is per- 
forated and covered with a layer of sand. In its 
passage through the interstices of the sand, a bad 
effluent is completely oxidised and becomes super- 
saturated with oxygen; if it be further treated in a 
small contact bed and again’ centrifuged, the puri- 
fication, both chemical and bacteriological, appears to 
be complete. The city analyst of Winnipeg found 
that the reduction of bacteria in a sewage effluent 
was from 8,150,000 to 1,150,000 per c.c., and that the 
B. coli were completely eliminated. 
A PROBLEM which is perpetually presenting itself in 
chemical work is to distinguish ‘‘mere”  poly- 
morphism from the more labile types of isomerism 
and polymerism. Perhaps the most conspicuous illus- 
tration is that of ice, which exists in several dense, 
as well as in one or more light, modifications; it is 
suspected that all the dense modifications may be 
polymorphous forms of dihydrol, H,O,, and that all 
the modifications which are lighter than water may 
be polymorphous forms of trihydrol, H,O,; but it is 
not easy to prove whether this view is correct or not. 
In the case of certain optically-active substances, such 
as the two varieties of glucose, conclusive evidence of 
isomerism or polymerism is found in the fact that 
freshly prepared solutions of the two forms exhibit 
unequal rotatory powers, gradually converging to a 
common value as a condition of equilibrium is 
attained; if the difference had consisted merely in the 
dissimilar marshalling of identical molecules in the 
crystals, every point of contrast would have dis- 
appeared instantly on dissolution or fusion. Unfor- 

