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THE CIVIL ENGINEER AM) ARCHITECT'S JOURNAL. 



[September, 



Tlie leiigtli of limber, tluis prepared, will luive two siJes opposite 

 T) each other with plain surfaces, one of the remaining sides grooved, 

 and the ci\\\n tongmd ; and in this state it is ready to to be cut into 

 blocks, to be laid down as street pavement. 



Simple as this grooving and toiigning may appear to be, thoy con- 

 stitute, in fact, a principal ]iart of the merit of the invention. The 

 fundamental principles of geometry have been strictly attended to iu 

 their construction, and the result is consonant with an adherence to 

 scientific laws. The tongues of one piece of timber fit into the grooves 

 of another ; and when two ))ieces arc thus united, the are not ftish 

 with each other, but the side of the second piece projects beyond the 

 side of the first to which it is fastened, exactly half its own width. If 

 a third length were attached to the second, in the same way that the 

 second was to the first, the edge of this third length would again pro- 

 ject beyond that of the second, half its width, and the same effect 

 would be produced with any number of pieces. 



The lengths, first prepared in the way described, will then have to 

 be cut into blocks. In order to facilitate information on this part of 

 the plan, we here introduce a diagram. 



fig. 1. 



Fia 



It will be observed there are two shaded parts, C and D, one at 

 each end of the length. These are cut to waste ; but the amount of 

 loss is so small as hardlv to be worth consideration in any estimate of 

 prime cost. With this'trifling exception, the whole of each piece, v.o 

 matter how long it may be, is brought into use. The dotted lines, 

 which intersect the length, indicate the direction of the saw when it is 

 converted into blocks. AAA are base-blocks, and B B B the key- 

 blocks. Let us, for the sake of an example, sup- 

 pose tjiat one length is cut into six blocks. Of 

 these, three are intended to be laid upon the ground 

 with their bases downward, and the other three to 

 form the surface of the pavement by reversing this 

 position, and placing their bases upward; and this 

 is the only distinction between the blocks of which 

 Mr. Rankin's pavement is composed. The lower 

 blocks are called base-blocks, and these support the 

 others; the upper blocl>s are called key-blocks, and 

 these firmly interlock the under blocks and them- 

 selves together. The annexed drawing, fig. 2, re- 

 presents the g/oond side of a base-block, a and b 

 being the grooves; and the engraving opposite fig. 

 :i, presents the loiigiud side of the same base- 

 block, a and B A being the tongues. The two similar 

 sides of the key-block are also exhibited in the 

 accompanying diagrams ; a and b in fig. 1, repre- 

 senting the grooves, and a in fig. .'> the tongue. 

 Such is the shape of the blocks of this most in- 

 Kig. 5. genious pavement; and begging 



our readers to bear in mind that 

 there are but two sets, upper and 

 lower, and that the individual parts 

 of every block of each set are geo- 

 metrically alike, we proceed to the 

 proof of its advantages, with the 

 promise of which we started. 



As " U.NCHANGEABLENKSS OF 



position" is a primary and most 

 important quality of this pavement, we will first explain how this is 

 secured. Fig. I! is a representation of five blocks locked together. It 

 will be noted that four of these are base-blocks, and but one a surface 

 block. If examined in detail, it will also be found that the key or 

 surface block is supported by the others, and by all equally; and that 

 no surface pressure can separate them laterally, or drive them asunder; 

 so that any weight applied at the surface, is distributed over a base 

 nearly four times its area ; but these lour base-blocks likewise respec- 

 tively lock in with four other dilTercnt series of the same kind, and so 

 on continuously from side to side of the street, where they rest on the 

 kerbs, and longitudinally from end to end of the pavement; and thus 



Fi;.' G. 



the weight applied to an individual surface block is not confined to the 

 four base-blocks, its immediate supporters, but is transmitted through- 

 out the whole structure, and no one part can yield to the superincum- 

 bent pressure, without causing a general deflection from kerb to kerb; 

 and as this is manifestly impossible, except to a small amount, it must 

 be granted, that the base of the pavement can never be affected, or 

 dislocated, by any tralfic whatsoever ; no inequality of surface, from 

 the sinking or depression of individual blocks, can consequently arise, 

 until the surface blocks themselves are fairly worn out, a residt which 

 is assuredly much more remote in wood than the public are yet pre- 

 pared to believe. The construction of this pavement, therefore, as 

 regards uniform stability of base, places it beyond all comparison with 

 any stone paving now in use, because it includes the principle of the 

 arch, the kerbs representing the abutting piers, and the upper or sur- 

 face blocks the key-stones ; and the greater the weight, the more solid 

 does the structure become by the tightening process of the wedge- 

 shaped key-bloeks, with their grooves and tongues. If our readers 

 will again examine figures 1 and 2, they will observe that the angular 

 terminations on two opposite sides of the base of every substratum 

 block (A — A) are chamfered or squared ; and if, furthermore, they 

 will suppose a row of these blocks to be placed on the ground between 

 two piers, or abutments, with their chamfered edges together, and the 

 upper blocks afterwards introduced in their proper place, it will at 

 once be evident that no sinking can take place without complete de- 

 struction of the parts. In truth, by this arrangement of shape, un- 

 changeableness of position is absolutely obtained. 



But, after all, the most important consideration in the adoption of 

 wood as a substitute for stone in the street-paving of the Metropolis, 

 will ever be the providing an effectual remedy against slu'PEKiness. 

 No pavement of wood, that does not offer a firm foothold for the horse 

 in all states of weather, will ever become generally adopted in London. 

 In every situation, whether in continuous motion, in backing, in being 

 abruptly pulled up or suddenly started, the horse must be able to main- 

 tain his feet in precisely the same place in which he places them down, 

 otherwise wood pavement will not have realised the grand advantage 

 of which it is susceptible. That nothing of the kind has been hitherto 

 accomplished, needs but a five minutes' examination of any public 

 street paved with wood immediately after and during the existence of 

 a passing shower. The plunging and sliding about of the animals are 

 then awful. If an omnibus going at the usual speed were suddenly 

 required to be stopped to take up a passenger, its momentum would 

 force the horses along the pavement several yards, in spite of all their 

 efforts to prevent it. In starting too, their feet rapidly slip from under 

 them for se\ eral moments before they can succeed in moving the vehi- 

 cle. Frequently they fall down and are injured, and the greatest pre- 

 cautions aie necessary under such circumstances to prevent accidents. 

 These things happen because there is no foothold for the horse in 

 damp weather upon any of the wood pavements hitherto introduced. 

 We can testify, of our own knowledge, that the reverse of this is the 

 fact in the case of Mr. Kankin's pavement. Indeed, it speaks for itself; 

 no argument is required to prove that the foot of a horse cannot slip 

 over its surface. At the same time it offers no resistance to the un- 

 interrupted progress of the wheel, and therefore a remedy against slip- 

 periness is not obtained by any sacrifice of facility of traction. A 

 general character of the paving may be gleaned from the annexed en- 

 graving. 



