This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
The London method of laying pavements is, first, to carefully grade the ground, sometimes using concrete to secure a firm foundation, where the soil is too soft; generally, sand spread over the level ground is considered good enough. The curbing is made of roughly "pene-hammered" grey granite, 12 in. wide on the top, and 6 in. high. Beside this run the gutters draining the roadway. The flagging is generally 3-4 1/2 in. thick. The edges are all squared, not being just pitched under, as is the practice in America. The edges are chiselled, not very elaborately, but sufficiently for the purpose, so that when the flagging begins to wear away, under the continuous traffic, the joints will continue good until it is threadbare, if ever it is allowed to remain long enough to get into that condition. A liberal allowance of mortar is thrown down on the sand in which to bed the stones. The stones are placed close together, the inspector of sidewalks generally demanding that the joints should not be more than 1/4 in. apart, and well filled with binding and hardening cement. The surfaces of the flags are machine-dressed, or rubbed, so that they always meet evenly at the joints. The rough stones are brought to the streets to be paved and are stacked in piles.
The pavers take them, preparing the edges with wonderful rapidity. They have a good way of splitting the flags: anything under 6 in. thick is broken in the same way that American marble-workers use to break up their slabs. American flaggers can break a stone very quickly, but no quicker than the English workmen, who also do it more neatly, and with less waste of material. A line is drawn on the face where a break is required; this is "strummed" in with a "pitching-tool" or "nicker"; the edges are also strummed in. Then the stone is smartly struck on the back with a round-faced hammer, 3 blows generally breaking it neatly down the lino. This method can be used by American flaggers, as it is successfully done with North River bluestone and with all kinds of sandstone in the brownstone cutters' yards, when cutting up sawn slabs for ashlar. Almost any kind of thin stone can be broken in this way, without the use of either wedges or plugs.
The pavements between the gutters are generally macadamized, although, as with us, stone and wooden blocks are used quite extensively. In the city proper most of the leading thoroughfares have recently been laid with a new patented preparation of asphalt. Asphalt-covered roads are a great improvement. The noise of heavy traffic is greatly diminished, and it becomes possible for pedestrians to hear each other speak without effort. At first this new system met with the unqualified approval of owners and drivers of horses; but complaints have recently been made that the least drop of rain renders the road so slippery that it is as bad as driving on ice, and the horses continually stumble and lame themselves. This could probably be obviated by sprinkling sand over the asphalt. It will require very strong remonstrance to induce the authorities to cease using the new material. Its two great qualities, cleanliness and quietness under heavy traffic, will outweigh a host of minor objections.
Near the opera-house at Vienna a small piece of the road is laid in the same way as that just mentioned. It is the best piece of road in the whole city. Asphalt pavements for interiors are also much used in Vienna. The finest example is in the hall of the Vienna Museum of Art and Industry. This is laid in different colours. The following is a translation of Suppantschitch's instructions for laying it.
(1) Bring your caldron as near as possible to the place where you intend to lay your floor, in order that you may lay it down as hot as you can get it.
(2) Put into the caldron 10-15 lb. of pitch; into the pitch put your asphalt. This latter must be placed in the caldron when the pitch is red-hot.
(3) The asphalt must be pounded into small fragments before mixing with the pitch.
(4) After the asphalt has been in the pitch 1 or 1 1/2 hour, stir it up well with an iron bar, broad at the end, until the asphalt is perfectly dissolved. Once this is done, fill the caldron with fine sharp sand; allow this sand to get warm for i hour by a good fire before mixing, so that it may of itself combine with the asphalt.
(5) Next stir up the contents of the caldron at short intervals. If the composition become stiff and difficult to stir, add a few lb. of pitch, using judgment as to how much.
(6) In laying it on bridges, thoroughfares, or viaducts, it is advisable to use more pitch, as the composition will then become more elastic. The asphalt will set without cracking.
(7) If, in stirring it, yellow vapours arise, that is an indication that the composition is ready for use. In order to prove the fact, make the following trial: dip a chip of wood into the composition, and observe if a greasy substance adheres to it; if such is the case, boil it more, until you are able to take the chip of wood out perfectly clean. The foreman must see that the ground to be covered is well swept, and clear of mud, damp clay, or any such substance. He then lays down iron rails, 3-4 ft. apart.
Those rails serve as a rest for the float used to make a level surface. One man attends to the caldron, another carries the prepared composition, in iron or wooden pails, to the operator. The workman who empties the caldron must not neglect to stir the contents of the caldron during this time, as the sand, being heavier than the pitch or asphalt, is liable to sink to the bottom, causing an uneven surface.
In order to produce asphalt in colours it is necessary to observe the following rules: - (1) A foundation of concrete, 1-1 1/2 in. thick.
(2) Float upon this a covering of black asphalt, 1/2 in. thick, as silicates will combine easiest with this.
(3) Put down thin wooden strips according to the pattern you desire to produce. These rails of wood should be cemented to the floor with hot asphalt.
(4) Then commence laying out the black part of the design. This should always be done first, as the black composition would be apt to soil the light colours if not laid down first.
(5) In order to make the edges straight and even, it is necessary to smooth them with the curling-iron, Fig. 1398. The wooden forms can be taken away when the composition becomes hard enough to stand without support.
(6) Once the design is all laid, commence polishing it with a piece of smooth sandstone attached to a handle, as shown in Fig. 1399.
(7) Production of artificial black: 40 per cent. chalk, 40 fine soft sand, 20 evaporated coal-tar.
(8) White silicate: 35 per cent. chalk, 35 pure white sand (silver sand), 22 pure white rosin, 8 tallow; first put the rosin into the caldron - it must be well melted; then put in your chalk; 1/2 hour afterwards mix in the sand; stir well and add the tallow. Asphalt in colours (red, blue, yellow, and brown) is to be boiled like the white composition, only adding the respective mineral colours.