326 CLAYS AND CLAY INDUSTRY. 



depending on the heat to be reached, size of kiln and the weather, 

 and after this several days are required for cooling. 



The absorption of the New Jersey fire bricks ranges in most 

 cases between n per cent, and 14 per cent. One sample of stiff- 

 mud manufacture showed 5.37 per cent., but other stiff-mud bricks 

 ran as high as 13.00 per cent. 



Their refractoriness is not as high as Ohio and Pennsylvania 

 bricks, and yet they have the reputation of standing changes of 

 temperatures much better. Each manufacturer commonly makes 

 three or four brands, which are adapted to special uses. 



TESTS OF NEW JERSEY EIRE BRICK. 



In order to test the refractoriness of the New Jersey fire bricks 

 and to determine its relation to their chemical composition and 

 texture, samples of their different brands were requested from 

 all the fire-brick manufacturers in the State. All except three 

 readily agreed to the proposition, and samples of the different 

 brands were taken from the stock piles or kilns by a member of 

 the Survey staff. The fusing point of the bricks was tested in the 

 Deville furnace and a partial analysis made to determine the quan- 

 tity of silica, alumina, ferric oxide and titanium oxide, the balance 

 being considered as lime, magnesia and alkalies. 



These tests are tabulated in the accompanying table. The 

 various samples are indicated by number (column at the extreme 

 left), and the name of the manufacturer is not published, but a 

 record has been kept in the Geological Survey office of the source 

 of each sample, and each maker has been supplied with a copy of 

 the tests made on his brick. 



Each column is properly headed and needs no explanation, ex- 

 cept, perhaps, the last two. The absorption represents the percent- 

 age of water absorbed by the brick when soaked for 48 hours, 

 and is, therefore, an indication of its porosity. The column 

 headed "Grade" represents the rank or quality of the brick as 

 compared with others made at the same works. Thus, all those 

 marked "1" come from different factories, and represent in each 

 case the best brick made at the factory from which they were 



