88 ANNUAL OF SCIENTIFIC DISCOVERY. 



form, of 15 inches by 13 inches in section, and 7 feet 6 inches in length, had 

 been found by the author to be as follows : 



The iron retorts lasting 365 days, and working off li cwt. of coal for each 

 charge, effected the carbonization of 2190 cwt. of coal, which, at 9000 cubic 

 feet of gas per ton, gave a total quantity of 985,500 cubic feet of gas per 

 retort; whilst the clay retorts lasted 912 days, carbonized 5472 cwt. of coal, 

 which, at 9000 cubic feet of gas per ton, gave 2,462,000 cubic feet of gas per 

 retort. It would thus be seen that the clay retorts yielded a greater quantity 

 of gas, from the same weight of coal, than the iron retorts ; but the specific 

 gravity of the gas so made was less, and its illuminating power was dimin- 

 ished, in consequence of the increased temperature of the clay retorts, which 

 caused the last portion of the gas to be decomposed. 



The most practical method of working clay retorts in large works was 

 with the addition of an exhauster. This reduced the pressure on the retort, 

 and prevented the escape of gas through the pores and fissures ; and by that 

 system the quantity made was increased about 200 cubic feet per ton of coal. 

 In small works, the expense of an exhausting apparatus, and steam ma- 

 chinery to work it, would not be compensated by the gas saved. 



HEATING BY GAS AND SAND. 



Some interesting experiments have recently been made in Albany, by Mr. 

 Calvin Pepper and others, to test the value of sand as a heating medium, 

 especially for railroad cars. The heat is obtained in the first instance by dif- 

 fusing the gas through sand. If the gas be directed into the body of the 

 sand, it will instantly diffuse itself through the entire mass, and rising to the 

 surface, may, with perfect safety, be instantly set on fire with a match, the 

 flame covering the whole surface of the sand with a pure flame without 

 smoke, no matter how large the extent of the flame, and with perfect and 

 complete combustion. The heat is almost instantaneously diffused through 

 the entire mass of sand, heating it equally throughout, and requiring but one 

 minute of time to heat the sand to such intense temperature that it will 

 retain its heat for hours after the gas is shut off and the light extinguished. 



INFLUENCE OF WALL-PAPERS ON THE TEMPERATURE OF 



APARTMENTS. 



Paper-hangings in themselves (says the Builder), as materials, maintain a 

 higher temperature than the walls or partitions on which they may be 

 placed; then less condensation of vapor takes place, and the dampness is 

 removed from the room as the progress of ventilation goes on. To a great 

 extent paper is an absorbent ; but then the moisture is given off in the same 

 form, or may escape by other means. The reason why dark papers are dryer 

 than light ones, is still due to the same action. All dark materials imbibe 

 more light and heat, and will thus maintain a higher temperature; besides 

 which, many of the very light-colored papers (particularly the better ones) 

 have a glazed or satin face, which is produced by the use of a large quantity 

 of China clay, a material that, from its coldness, at once causes condensation 

 of moisture, and thus facilitates its own decay. 



SUBSTITUTE FOR LEATHER. 



Samuel Whitmarsh, of Northampton, Mass., has invented a new fabric 

 which is intended to supply the place of leather in many of its applications. 



