Double block.
We give also figures of two useful forms of double block. No. 5, on which the sheaves are side by side, is called a sister block. No. 6, in which they are one above the other, is a fiddle block. Notice that in this form the lowermost sheave is the smallest, and thus the rope passing over it is not jammed by the one that passes over the upper.
MAKESHIFT LATHES.
Makeshift lathes
In the manufacture of a number of wooden articles, such as the sheaves of blocks, bowls, round balls, &c., the aid of a makeshift lathe will be required. There are several forms of lathe made use of in different countries. No. 1 in the annexed illustration is the best we know of for the use of the traveller or explorer. To make a contrivance of this kind proceed as follows: Prepare three squared posts, bore an auger hole through the top of each at about 5in. from its head; to these holes fit a spindle made of some hard tough wood, in such a way that it will just easily play round in the holes without shaking about; cut a slice from a log about 7in. in diameter; trim it until it is quite round; cut a tolerably deep groove round the edge, and bore a hole in the centre for the spindle to come through. Now, from a piece of pointed iron rod or bar make a pivot pin, as shown passing through the head of the post which stands alone; fit this in the hole so tightly that the driving of a single wedge prevents it from sliding forward or back. All the posts must be firmly fixed in the ground at an even depth, and at the relative distances shown in the engraving. In the end of the spindle opposite the pivot pin three sharp iron spikes, made from nail points, must be driven; these hold the work in its place when revolving. This it is made to do by the action of the spring overhead, which is usually made from a tough elastic pole or bamboo cane. The end of the spring is fitted with a long strip of hide or a rope, which, passing once round the grooved slice of log, is attached to the end of the treadle. This is made from a naturally-forked branch, with a bit of plank lashed fast to it for a foot board. The chisel rest is made by driving a post into the ground in front of the work, making a saw-cut in its head, and then driving a bit of thin board or a piece of broad hoop iron into it, in the form of the letter T. The spindle is prevented from moving too far back by having pins driven through it before and behind the tail-post.
The lathe represented at Fig. 2 is common throughout the East. It is by the use of this contrivance that we have seen the long and beautifully straight pipe tubes, for which Stamboul is so justly celebrated, made. We have also seen the turners of Poona, in India, making their wonderful nests of almost air-tight boxes by the aid of the bow-lathe (Fig. 2). It is erected much on the principle of Fig. 1; but is usually placed so close to the ground that no one but an Asiatic could work conveniently at it.
Grinding stones, to mount.