—The cost of obtaining natural rock asphalte from the mines, and the knowledge that it is composed of two very simple ingredients, limestone and bitumen, has led to a great number of artificial asphaltes being introduced, especially for foot pavements. “British Rock Asphalte” is a name by which many of the compositions are known; “Beauchamp’s Mendip Mountain Machine-made Granite Asphalte” is a high-sounding title; “Prentice’s Mineral Foreign Rock Asphalte” is another.
All these, and many more of the same description, are really what may be better and more correctly described as “tar concrete” or “tar paving,” and consist of different modifications of the homely coal-tar and limestone.
So long ago as the year 1840, “Lord Stanhope’s Composition” was well known; it was made as follows:
Three gallons of Stockholm tar, 2 bushels of well-dried chalk, 1 bushel of fine, sharp, clean sifted sand, the whole being boiled in an iron caldron.
Tar paving is now made in many and various ways by different surveyors of towns, some making it with hot compositions, some with cold. A description will be found in the chapter on Macadamised Roadways, page 46, of one method of making it, a modification of this being all that is necessary for foot pavements.
The best paths of this description that I have seen are to be found at Torquay, and by the kind permission of Mr. John Little, County Surveyor of Devon, and late Surveyor of Torquay, I give his useful specification in detail, as follows:
Tar Concrete for Footpaths.
Proportions of Materials.
| 12 | barrow | loads of | engine ashes. |
| 4 | „ | „ | screened slaked blue lias lime. |
| 4 | „ | „ | small spar or sharp grit. |
| 34 gallons of best gas tar. | |||
| 20 bucketsful, say 70 to 80 gallons of water. | |||