I ought to remark that in all formulas which I use, _Para rubber is used_, which is now nearly _four times the cost of Java_, and is frequently more. This circumstance has for some time been attracting the attention of manufacturers, and bids fair to shut out almost the use of the former in all goods confined in moulds to vulcanize. I would call the especial attention of engineers to this fact, as Java materially reduces the cost, and needs very little judgment on their part to adopt it in these forms, in place of the expensive kind. I do not say it is so strong a gum as Para, but I feel certain that the manufacturers will be awake, and use it, without perhaps yielding the advantage out of their own factories, and therefore it is necessary for consumers to try how far they can “assist themselves” without their benevolence, especially as “Java gum” is now so readily and cheaply cleansed of all dirt or gritty matter. These remarks apply to the recipe I now hand, which is termed—best pure spring, or washers, &c. Grind together 30 lbs. Para Gum, 5 lbs. Oxide Zinc, 2 lbs. Carbonate Magnesia, 3 lbs. Common Chalk, 2 lbs. Porcelain or Cornwall Clay, 30 oz. Pure Sulphur. This costs about 33 cts. per lb. and is sold at $1 per lb., and though heavier, is intended to meet Messrs. Mackintosh and Co’s. article at $1 12½. The difference in density renders the latter the cheapest to the consumer, while the reduced price of the former catches the unsuspecting trader in these goods, and frequently obtains his preference. The companion quality to the above for large valves, and packing sheets, is made as follows, and is styled—best pure packing. Grind together 30 lbs. Para Rubber, 5 lbs. Oxide Zinc, 5 lbs. Porcelain or Cornwall Clay, 28 oz. of Pure Sulphur. This costs about 31 cts. per lb. and is sold at $1 per lb., and is a trifle heavier than the pure spring quality. It will be perceived that sometimes pure sulphur is used, and sometimes the common flour of sulphur; the former is thought to render the goods more soft and velvety, but the difference in their relative cost is very wide, and the writer will not undertake to say how far the marketable value of the goods is improved, but thinks it will be admitted that their intrinsic value to engineers is not altered in any way.