SCIENTIFIC SUMMARY. 
433 
the law of expansion of superheated steam have been published, and con- 
firm the surmise stated in a previous paper, that at temperatures consider- 
ably above the point of saturation, or at which steam is of the density 
which it would assume in contact with water, the law of expansion is 
identical with that of air and other permanent gases. Near the saturation 
point, the rate of expansion is much higher, and it diminishes rapidly as 
the temperature increases till the mean value of the constant E in the 
common formula becomes 458 '74, that for air deduced from the experiments 
of Regnault being 459, and that assumed for a perfect gas by Rankine 
being 46 1‘2. 
Steam Sledge. — M. Routzen has matured a system of steam transit for 
the snow-covered roads of Northern Russia during the winter months. 
He employs a train of sledges, one of which carries a high-pressure 
engine, boiler, and windlass. The train is hauled forwards by cables 
attached to fixed anchorages, and the rate of progress does not exceed a 
mile an hour. 
Aluminium Bronze, to which we have already referred, has been selected 
by Lieutenant-Colonel Strange as the material for the construction of the 
great Theodolite for the approaching trigonometrical survey of India, on 
account of its high tenacity (45 tons per square inch, twice that of ordinary 
bronze, and equal to that of steel), its great rigidity or resistance to flexure, 
and its unoxidability. Sterro-metal, the new alloy employed in Austria 
for guns, and containing If per cent, of iron, has nearly equal advantages.* 
MICROSCOPY. 
The Colouring Matter of the Red Sea. — Mr. Id. J. Carter, of Bombay, 
who returned to England last June, after spending many months on the 
coast of Arabia, had an opportunity of seeing the colour of the Red Sea 
which is produced by Trichodesmium Ehrenbergii , an oscillatorian vegetable 
organism, first described by Ehrenberg in 1826. Mr. Carter describes it 
as a yellowish-brown oily-looking scum on the surface of the sea in large 
areas of many miles in extent ; and once he saw a portion of brilliant red 
and one of intense green together in the midst of the yellow. The odour 
was like that of putrid chlorophyll, well known to those who have much to 
do with filamentous alga:. Having collected some of this scum in a bottle, 
by the aid of a lens he found it to consist of little short-cut bundles of 
filaments, like Oscillatoria. Under the microscope, specimens preserved in 
alcohol — the bundles in which were about in. long by in. broad — 
were found to contain about 25 to 60 filaments, each about T V i n - long 
and in. broad. The bundles bore no evidence of an investing sheath, 
but of the filaments being held together by mucus secreted from them 
generally. The yellow colour is most prevalent, the red next, and the 
green least of all. The red colour, like the green, appears to herald the 
See also Summary of Metallurgy. 
