Sometimes the Para gum is used in this mixture; but, though better, its use is not considered imperative if the Java caoutchouc is well cleansed. A cured coat, well vulcanized, is a great improvement in all respects upon the filthy naptha or varnish coat, and should, when competition is thrown into the market, exceed it very little in charge. As long as the calico upon which these are run is covered, the thinner that covering the better; and by far the best I have seen are made by Messrs. Mackintosh and Co., Moulton & Co., Moses, Son & Davis. I have seen some very bad ones, ill-shaped, non-vulcanized, and altogether only useful _in bringing the better make into unjust dislike by the public_. The sooner these latter daubs are improved, or withdrawn from sale, the better for the reputation of the India-rubber garment dealers. The cloth upon which the material is spread weighs about four ounces by the yard, and therefore the quantity of gum on each article is readily assessed, and the scale will determine which are lightest and best for a storm. The article termed “sulphuret of lead” in the formula, is the chemical I have before remarked upon, and the screen or blind, nick-named (_for reasons therein explained_) “hypo,” and is only useful in so far as _it is an excellent black pigment_, which is only of importance in the garment branch of the trade. ADULTERATION OF INDIA-RUBBER, IN CONNECTION WITH THE MANUFACTURE OF INVALID WATER MATTRESSES AND CUSHIONS. There is no necessity for the monstrous charges at present made for these goods, and hence I desire to open up the subject fearlessly. The amount of adulteration necessary to bring up the desired color, is from 4 to 10 per cent. of the pigment termed _oxide of zinc_; but the formula used for the manufacture of the water or air mattresses and cushions referred to, contains about _thirty-five per cent. of this cheap substitute for India-rubber_. In writing thereon I take leave to state at the outset, that, like the “air,” or Mackintosh cushions or pillows we have known for so many years, they can be had of any size or shape, and differ from them in being of pure caoutchouc, or elastic gum, (_minus the adulteration_) instead of only a _thin coating_ of pure gum, upon a cloth or non-elastic foundation. Hence their increased value to medical men in preventing bed sores, &c.