The mineral asbestos is but a very poor packing material in steam-boilers. Moreover, it acts as a strong grinding material on all moving parts.

For some years I have tested the applicability of artificial precipitates to close the holes in boilers, cylinder-covers, and stuffing boxes. I took, generally with the best success, alternate layers of hemp-cotton, thread, and absorbent paper, all well saturated with the chlorides of calcium and magnesium. The next layers of the same fiber are moistened with silicate of soda. By pressure the fluids are mixed and the pores are closed. A stuffing box filled with this mixture has worked three years without grinding the piston-rod.

In the same manner I close the screw-thread hole in gas tubes used for conducting steam. I moisten the thread in the sockets with oleic acid from the candle-works, and dust over it a mixture of 1 part of minium, 2 parts of quick-lime, and 1 part of linseed powder (without the oil). When the tube is screwed in the socket, the powder mixes with the oleic acid. The water coming in at first makes the linseed powder viscid. Later the steam forming the oleate of lime and the oleate of lead, on its way to the outer air, presses it in the holes and closes them perfectly.

After a year in use the tubes can be unscrewed with ease, and the screw threads are perfectly smooth.

With this kind of packing only one exception must be made--that is, it is only tight under pressure; condensation or vacuum must be thoroughly avoided.--Chem. News.