On The Testing And Strength Of Railway Materials, &C

bo 3601 b ., because , unfortunately , some have broken at 36 Glb . " Mr . Haivkes experiments ivere to ascertain the transverse strength of bricks , not their power to resist a crushing force . It is important to know for how long a brick will carry a weight without breaking . We are told that one common Boston brick which broke with a weight of 9201 b ., sustained a pressure of 6901 b . for forty-eight hours , and then broke ivith a weight of 1 , 3301 b . ; of course these experiments were made upon the half brick , and

calculated out at the standard size and bearing . A brick from dried ground clay by pressure sustained a weight of 8201 b . for forty-eig ht hours—its original strength being 8981 b . —and it broke when the iveights were made up to 9501 b . Half ' bricks frequently require a greater iveight to break them than whole bricks . Taking twentyfive bricks each from different districts , it was found that theaverage iveight ivas 7 'Solb ., and the strength usually increased with the weight . We gather from Mr . Hawkes ' tables of experiments the folloiving useful facts ;—

Boston red bricks , best . These bricks are ivell made , ancl have a smooth surface , and are straight and square at the edges . They cost in Boston 17 dollars per thousand . Mean strength , 5 , 0641 b . Common Boston bricks , of a dark red colour , labour at 2 dollars per thousand , are free from rubbish . Mean strength , 3 , 1841 b . Baltimore best bricks are hand-made . The very best sell at 25 dollars per thousand , ancl ordinary bricks at from 6 to 8 dollars . Mean strength , 3 , 5511 b . Common Baltimore bricks are considered to be far stronger than stone—the bricks from old buildings

being very sound . Mean strength , 3 , 0401 b . The Dutch bricks were furnished by Messrs . Rosher , of Holland Street , London . Greatest strength , 4 , 0001 b . ; mean strength , 3 , 5801 b . The Dutch clinkeis are stronger aud heavier than American common bricks . The clinkers " are made at Moor , near Gouda , in South Holland , from the slime deposited on the banks of the River Yssel , and formerly from that of Haarlem Bleer . The colour is a light yellowish brown . The clay or slime is ivashed to get rid of the earthy matter before being moulded . ' '

From the experiments made on home-made bricks we gather these interesting facts : —The Tipton blue bricks give the greatest strength ( 5 , 5531 b . ) , the mean strength being 3 , 9751 b . Best Garrison Lane , Birmingham , bricks , ivhich are hand-made , the clay being passed only through one pair of rollers , stand next in order . Greatest strength , 3 , 5301 b . ; mean strength , 3 , 3761 b . ; ivhile the common bricks from the same neighbourhood were far inferior . The bast Oldbury bricks gave the greatest strength at 46001 b . ; the mean strength being 33451 b . ; while the common Oldbury bricks stood

, , at 3 , 3611 b . greatest strength , and 2 , 1931 b . mean strength . These bricks were manufactured by Messrs Barnsley ; those made by Messrs , Ingram by machines gave the following results : —Greatest strength , 3 , 7031 b . ; mean strength , 3 , 1201 b . ; the least strength being 2 , 0781 b . Messrs . Bradley and Gavau ' s machine-made bricks ,

manufactured in Leeds , gave the greatest strength , 4 , 1331 b . ; mean , 3 , 1981 b . ; least , 2 , 6161 b . The clay is taken from the pit , aud does not undergo any previous preparation . In some cases no water is added . The hand-made bricks had a moan strength of 1 , 0381 b . Some bricks from' Bri'dgewater were tried aud found to give the greatest strength , 3 , 2001 b . ; mean , 2 , 3181 b . ; and least , 1 , 5151 b . Crickmay ' sbricks ( near Weymouth ) , handmade , one pair of crushing rolls , but no pug-mill : —Greatest strength , 2 , 6801 b . ; mean , 1 , 9401 b . ; least 14801 b . ; while some bricks made in two yards nearer Weymouth only

, , gave the mean strength of 7251 b . White bricks made in Leicestershire : —Greatest strength , 1 , 4721 b . ; mean , 1 , 1041 b . ; least 8241 b . Oxford bricks : —Greatest , 1 , 1871 b . ; mean , 1 , 0871 b . ; least , 8751 b . Two lots of London ( stock ) bricks ivere tested , and gave the following results : —No . 1 : Greatest strength , 1 , 4961 b . ; mean , 9981 b . ; least , 3661 b . No . 2 : Greatest , 1 , 3961 b . ; mean , 8251 b . ; least , 4851 b . Prior to the commencement of the Avorks in connection ivith the Southern Main

Drainage , Mr . Grant , the engineer , made a series of experiments on the compression aud strength of various bricks . These experiments ivere made about the same time as the testing trials ivith the Portland Cement used for these works , and ivhich have been described in Building News . 300 experiments ivere made on the strength of bricks , ancl some useful facts were ascertained . From the six tables in ivhich these facts are 2 N