The paint successfully used for the canvas roof over the tubes of the Britannia Bridge was composed as follows : - Coal tar, 9 gallons; slaked lime, 13 lbs.; turpentine or naphtha, 2 or 3 quarts - the whole being dredged over with sand. The addition of the quicklime is indispensable to neutralise the free acid that exists in the tar.

A tar paint recommended by Mr. Hurst as the best protection for iron consists of 1 gallon coal tar distilled to expel the watery vapour and naphtha, and afterwards mixed with \ pint naphtha and 1/2 pint boiled oil.

Ordinary Tarring

Boil 6 gallons Goal Tar with 1 lb. resin, 1 lb. pitch, and apply hot; or use Stockholm Tar, with the same proportion of pitch only. Yellow ochre may be added to give a brown tinge.

Silicate Zoppisa, sold by the Granitic Paint Company, is a washable distemper made in all colours; it is said to dry hard and fiat, and to render the surface to which it is applied damp-proof and durable.1

Asbestos Paints are much used for internal rough woodwork, which they will protect against sparks or light flames, but they cannot stand the weather. They are, as a rule, mixed with oil in two coats, and are thinned when necessary with warm water.

One gallon will cover 150 feet two coats.

1 Circular. 3 Matheson.

2 Seddon. 4 Davidson.

Asbestos Oil Paints are also made, and it is claimed that their covering power is greater than that of ordinary lead or zinc paints.

One cwt. in fact when thinned will cover 600 square yards. One cwt.. Bent out ready for use will cover 480 square yards.

Crease's Antiwater Enamel Paint for iron is a sort of silico-calcic cement It adheres to iron fairly well, especially when the iron is nearly always submerged in water.

Crease's Anticorrosion is a black bitumen paint useful for coating submerged iron surfaces.

Granulated Cork Paint is applied over paint to protect and roughen surfaces upon which the condensed moisture of the atmosphere is likely to deposit, such, for example, as the asphalte floors of cellars, paved ceilings and the girders supporting them.

Coating floors. - For asphalte floors the composition is made and applied as follows : - 4 parts (by weight) of Venetian red and 1 part of red lead are mixed into a stiff paste with Stockholm tar and well worked together. It is then laid on the surface of the asphalte about 1/8 inch thick, and 3/8 of the granulated cork is sprinkled over the paint and pressed in with a float. In about 48 hours the composition is hard, and the loose cork can be brushed off. As the granulated surface will not withstand wear, it must be protected by open boardings or by gratings.

For surfaces overhead, such as slabs or iron girders, ordinary red lead paint is used as a matrix for the granulated cork, which is forced into it and then painted over.