This is brown at first, but in a few days the sulphur blows over the surface grey or white, and would lead an amateur to judge they were of that color throughout. Buffer springs and other moulded goods from this compound are a little heavier than Messrs. Mackintosh and Co.’s. A density railway spring, at 4_s._ per lb. gross, and were made at first to meet it, also sold at 2_s._ 6_d._ per lb. net. It is a most useful spring, and in competition should be bought at 1_s._ 3_d._ to 1_s._ 6_d._ per lb. net, but I should strongly recommend that engineers try a substitute of all “Java gum,” by obtaining a few _away from their usual manufacturer_, ON TRIAL, as I believe their quality as a spring would not be injured, and the price would be reduced, and, moreover, it would guard against the manufacturer being left tempted to do so, without reducing the charge. For the guidance of engineers, I remark, that a spring of this quality and dimensions, 4½ × 2½ × 1, pressed to half an inch, showed 3½ tons on the dial, and one with equal quantities of oxide of zinc and magnesia, of same size, &c., indicated 1½ tons on equal pressure, while the quality of Mackintosh and Co.’s, referred to before, and of which this was an intimation, marked 1¾ tons on the dial; of course, a spring with a smaller bore than 2½ inches would show greater tonnage. The next recipe is for grey packing, which is largely and exclusively used by some dealers for marine engines, &c., as well as in sheet; and if the price (3_s._ 6_d._ per lb.) was not _excessive_ for so much adulterated matter, I would pass it over in silence as a very fair and useful article, and if approved, my form will enable the engineer to obtain it much cheaper by competition. Say then, Grind together 25 lbs. Para Rubber, 5 lbs. Cleaned Java, 16 lbs. Oxide of Zinc, 6 lbs. Carbonate of Magnesia, 3 lbs. Porcelain or Cornwall Clay, 2 lbs. Red Lead, 30 oz. Pure Sulphur. So that it costs 25 cts. per lb., and hence I submit that 75 cts. per lb. is _excessive_, with discount from 10 to 20 per cent. Unless the magnesia in this packing is well calcined it will cut porous, but does not show its valves cut to shape before vulcanizing. It may seem I lay too much stress upon high prices, and if the goods were bought in trifling quantities, it would carry argument; but as the orders are usually large, and show good monied invoices, there is a wide margin for reduction; besides in many cases these long prices prohibit the use of caoutchouc. _The prices are about right if the goods were of pure India-rubber_. * * * * *