These looms often are speeded as high as 180 picks per minute. To operate at this speed with so many pieces of web and make satisfactory goods, free from thick and thin places through irregularities of speed or variable momentum in running, a very heavy type of loom is necessary. They should be erected on solid foundations so as to eliminate all possible vibration. A solid concrete floor into which timbers have been properly set so that the feet of the looms may be securely anchored into them is the ideal way, but where this is not practicable at least heavy foundation timbers for anchoring the loom feet to should be arranged. The frames of the looms should be heavy; also the main driving shaft, which should have wide bearings so as to prolong the life of the shaft at the wearing points and obviate loose play in the boxes. The crankshafts must also be very heavy and there should be enough of them so as to rigidly withstand the repeated beat of the lay without liability to take on any loose motion, which would be fatal to the production of perfect goods. Weight and strength here is very essential, inasmuch as it is not practical to get a direct line from the shaft to the lay on account of the harness movement, and they must be built to drop below the harnesses which form makes them subject to heavy strain at the beat of the lay. They should also be made adjustable, each arm having a heavy left and right threaded insert, so that the length of the weaving line may be changed to meet the varying requirements of different webs. They should also be constructed so that any wear may be taken up. The lay itself must necessarily be very heavy. It is generally constructed of several thicknesses of timber of different kinds, so as to avoid any possibility of warping and shrinkage. The shuttles used are mostly made of applewood. While they must run smooth and be free from the risk of slivers they must at the same time be very light so as to be freely drawn across the multiple of web spaces. It will be easily seen that the drawing of so many shuttles over a space of about three times their length, at possibly 180 picks per minute, carrying and delivering the necessary weft to the webs, each thread of weft being checked to a certain extent by friction springs, requires great care and thought in construction. Shuttle wood must be thoroughly seasoned by age or it will not serve the purpose.