原创 Abercrombie Outlet427

Abercrombie Outlet427

The portion a Y of the arch is joggled like the upper part. The interior part is filled up with large blocks of Kentish rag, forming a kind of coursed rubble-work, the courses tending to the centres of the arch. The under corner of each arch stone projects Abercrombie and Fitch over the one below it. By this form it takes fast hold of the rubble-work behind it. Above this rubbTe there is constructed the inverted arch 11 G of Portland stone.* This arch shares the pres?sure of the two adjoining arches, along with the arch stones in Y a and in G b. Thus all tend together to com?press and keep down the rubble-work in tbe heart of thi* part Abercrombie Outlet of the pier. This is a very useful precaution ; for Abercrombie and Fitch Outlet it often happens, that when the centres of the arches are struck, before the piers are built up to their intended height, the thrust of the arches sqneezes the rubble- work, horizontally, after the mortar has set, but before it^has dried and acquired its utmost hardness. Its bond is broken by this motion, and it is squeezed up, and never ac?quires its former firmness. This is effectually prevented by the pressure exerted by the back of the inverted arch.Above this counter arch is another mass of coursed rubble, and all is covered by a horizontal course of large ' blocks of Portland stone, butting against the back of the arch stone ZI and its corresponding one in the adjoining arch. This course connects theieet of the two arches, pre serves the rubble-work from too great compression, and protects it from soaking water. This last circumstance is important; for if the water which falls on the road-way is Abercrombie not carried off in pipes, it soaks through the gravel or other rubbish, rests on the mortar, and keeps it continual]/ wet and soft. It cannot escape through the joints of good masonry, and therefore fills up this part like a funnel. , Supposing the adjoining arch fallen, and all tumbled off ^hat is not withheld by its situation, there will still remain in the pier a mass of about 3500 tons. The weight of the portion VY is about 2000 tons. The directions of the thrusts RY and YF are such, that it would require a load of 4500 tons on VY to overturn the pier round F* This exceeds V Y by 2500 tons; a weight incomparably greater than any that can ever be laid on it.