96 
POPULAR SCIENCE REVIEW. 
The new researches seek to determine the motion of the liquid threads, that 
motion varying with the depth when water flows over a plain surface. 
These researches are too technical to he described here, but as they are of 
very great importance both practically and theoretically, it may be useful to 
mention that a translation of the abstract appended to Colding’s paper has 
been printed. Colding has applied his results in the study of ocean currents. 
Floating Breakwaters. — Mr. T. Cargill has proposed the use of a particular 
form of floating iron breakwater, in preference to the immense expensive solid- 
masonrv structures now employed. He supposes the influence of the waves 
not to extend to a greater depth than 15 feet from the surface. To break 
the force of the waves he proposes an iron floating structure composed of 
sections each 100 feet in length. Each section is in the shape of a triangular 
wedge with the apex towards the sea. The wedge is right angled and has 
one horizontal and one sloping surface. The horizontal surface is nearly 
level with the water. The section is composed of a series of screws of 
lattice wrought-iron framework. The theory is that in passing through 
these screws the waves would be gradually disintegrated and strained of 
their violence. The idea of floating breakwaters is not new, and many plans 
of such structures have been proposed, and in one or two cases they have 
been tried, but without success. Nothing but experiment can determine 
whether Mr. Cargill’s designs would accomplish the end proposed in a 
practical manner. 
Domestic Steam Engines. — MM. Mignon and Rouart, of Paris, are sup- 
plying, on the system of M. Fontaine, a small domestic steam-motor, of 
to 1 horse power. They are intended to be employed in driving lathes, 
sewing-machines, pumps, jewellers’ tools, &c. If the use of these engines 
becomes general, it will affect many industries by enabling the workmen to 
labour at home at a variety of employments which now are carried on in 
large shops. The steam is raised by gas. The boilers are vertical tubular 
boilers, with Bunsen burners. The products of combustion can be led to an 
ordinary chimney. The boiler holds water enough for several hours’ work, 
so that it does not require constant feeding, but can be filled up twice a day. 
There is a self-acting arrangement for regulating the gas flames. The 
machine weighs about 2 cwt., and costs 500 francs. — Paris Correspondent 
of 11 Engineering.” 
Strains on Arches. — Mr. W. Bell has communicated to the Institution of 
Civil Engineers a paper on the determination of the stresses in metallic 
arches under unsymmetrical loads by combining graphic methods and calcu- 
lation. The paper is one of great interest. 
Pneumatic Despatch. — At the Institute of Civil Engineers, Mr. Siemens 
read a most interesting paper on his system of pneumatic despatch tubes 
now in use in Berlin, and also in London between the General Telegraph 
Office and Charing Cross. Mr. Siemen’s system differs in principle from 
that originally introduced by Mr. D. K. Clarke. On Mr. Clarke’s system a 
single tube was used between any two points, the carriers containing the 
messages being blown through in one direction and drawn back in the other 
by exhausting the air before them. Hence, in this system, the direction of 
the current of air is reversed at intervals. On Mr. Siemens’ system a pair 
of tubes are laid down, one taking the carriers in one direction, the other 
