Chap. VIII.

BRITAIN.

375

paste, he gradually added the

at a time, to which, when formed with sea-water into a thinpuzzolana, and at the same time kept continually beating it.

When the mason had fitted the stone to its place, it was hoisted by a light movabletriangle, furnished with a double tackle; then properly bedded, afterwards beat down witha heavy wooden maul, and levelled with a spirit level.

The carpenter then placedthe oak wedges in the groovesprepared for them, one uponits head, and the other withits point downwards, so thatthe two wedges were headand point together; then, bymeans of an iron. bar, 2Jinches broad, | inch thick,and 2^ feet long they weredriven down one wedge uponthe other, very gently at first,so that the opposite pair ofwedges being equally tight-ened, would equally resisteach other, and the stone,therefore, keep its place; asthe wood, when first inserted,was in a dry state, by itsswelling with the moisture,it became tighter. To pre-vent the stones from beingbroken by driving thesewedges, a couple of otherswere pitched at the top ofeach groove, the dormantwedge, or that with the pointupward, being held in thehand, while the drift wedge,or that with its point down-wards, was driven by thehammer ; the whole that re-mained above the surface wasthen cut off with the saw; acouple of thin wedges werealso moderately driven at thebutt end of the stone, thetendency of which was toforce it out of its dovetail;these were calculated to unitethe mass, and prevent anyviolent agitation of the seafrom displacing them.

The oak wedges servedeffectually to bind the stonestogether in their severalcourses; but to preventtheir being lifted up be-fore the mortar becamehard, oak trenails wereused. A couple of holes,lj inches in diameter, werebored on shore, throughthe external or projectingend of each stone; afterthey were placed, and thewedges fixed, one of thetinners, or Cornish men,with a jumper continuedthe hole into the course

below, and bored it about 8 or 9 inches in depth; but the lower hole was not so large indiameter as the one above by J inch. The trenails, being nicely planed down to drive freely

b b 4

Fig. 380.

EDDYSTONB LIGHTHOUSE.