1872.] Enginecring. 525 
the side of the fire-box of the locomotive, having a steam-cylinder and an air- 
cylinder, by means of which the air is compressed into a reservoir, placed 
beneath the foot-plate, and having a capacity of about 12 cubic feet. From 
this reservoir the air is led by a pipe to a three-way cock, placed so as to be 
conveniently under command by the engine-driver, the two other branches of 
the cock communicating the one with the atmosphere, and the other with a 
pipe leading to a duplicate line of pipes running under the carriages the whole 
length of the train, by which the compressed air is led to the brake ma- 
chinery. These latter pipes are connected together between the vehicles by 
means of lengths of india-rubber tubing. Under the tender, and under each 
carriage to which the brake is applied, is placed an air-cylinder with a piston 
working inside, the piston-rod from which communicated with a thrust-rod, 
and through it the pressure of the air upon the piston is applied to the brake 
gear. By the adoption of a special mode of conneétion the brakes are left 
free for application by the ordinary hand apparatus, if necessary. The appli- 
cation of the brakes is effzcted simply by turning the three-way cock above 
referred to, so as to admit compressed air from the reservoir into the lines of 
pipes extending through the train. The air thus admitted into the pipes 
passes into the cylinders, forces out the pistons, and thus, through the inter- 
vention of the thrust-rods and brake gear, exerts the requisite pressure on the 
brake-blocks. During a recent experimental trip on the South-Eastern Rail- 
way—the train consisting of an engine, tender, and six carriages—the brake 
was first put on at.a time when the speed was 30 miles an hour, and the train 
was stopped in 18 seconds, and in a distance of 149 yards, up a gradient of 
Iin 142. The second stop was made on a rising gradient of 1 in 120, the 
speed being the same as before. In this case the time taken in arresting 
movement was 16 seconds, and the distance 107 yards. The speed of the 
train was 55 miles an hour when the third stop was made, on a falling gradient 
of r in 120, the time required from the moment of applying the brake to 
stopping the train being 32 seconds. On the fourth and last occasion the 
speed of the engine had been increased to about 60 miles an hour at the 
moment of putting on the brakes, and the train was brought up in a distance 
of 400 yards, the road in this case being tolerably level. 
Portland Breakwatey.—The completion of this magnificent work was in- 
augurated by His Royal Highness the Prince of Wales, on Saturday, the 
roth day of August last. So far back as 1794 the first conception appears to 
have been entertained of the advantages that would be derived from the con- 
struction of a breakwater at Portland, but it was not until fifty years after- 
wards that any active steps were taken towards the accomplishment of that 
object. In 1847 an Act was passed authorising the construction of the break- 
water, and the preliminary works were commenced in the same year. The 
work of constructing the breakwater was practically commenced in 1849, from 
designs by the late Mr. Rendel, Mr.—now Sir John—Coode being the resident 
engineer. On the 25th of July, in the same year, the Prince Consort laid the 
foundation-stone, and ten years later the works were so far advanced as to 
afford a safe anchorage during a storm. The Portland breakwater works 
commence with a pier, which starts from the island of Portland near the point 
where it is connected with the mainland by the Chesil Bank. This pier runs 
due east for a length of about 1900 feet, at which point there occurs an 
opening 400 feet wide, and having a minimum depth of 45 feet, to admit of 
the entrance of ships of war of the largest class from the southward. On the 
other side of this opening the breakwater proper commences, and is carried 
out to sea for a distance of 6000 feet, from its starting-point. 
The pier, or inner breakwater, consists of a rubble mound, composed of 
stones of all sizes. After the mound had been consolidated, a trench was 
excavated within it to the level of low water at spring tides, and a wall of 
masonry was erected therein. The face-courses of this wall, up to 6 feet 
above high-water level, are hewn granite. The sea-wall is strengthened by 
counterforts, 20 feet apart, and conneéted by arches, so that a platform is ob- 
tained 15 feet in width, exclusive of the footway and the parapet. The 
breakwater proper is simply a rubble bank, the material of which it is 
