by hand, or may be guided by means of a pantograph. The figure having been thus traced on the roller, the latter is plunged into a bath of nitric acid, which cuts into the metal at all points where the asphalt coating has been displaced. Finally, the asphalt is washed off with essence of turpentine.
But the figures are usually produced on the roller by means of the molette. This is a small cylinder of steel, into the surface of which the engraver first cuts the design. This cylinder then gives to another an impress in relief; and, finally, from this latter a concave impress is taken on the large copper roller of the printing-press. It is plain that as many rollers will be required as there are colors to print; and, owing to the difficulty of preventing the colors running into one another, not more than four are commonly employed—black, red, rose, and violet; or black, brown, red, and cashew. In twelve hours, 100 to 120 pieces, of 50 yards each, may be printed in one color, though not more than 60 to 80 could be printed in four.
The capital employed in the manufacture of printed goods of mixed fibre is enormous, and yields a large return. This manufacture gives also good remuneration to the operatives, and there is every reason why it should be as zealously fostered as the manufacture and employment of muslins and calicoes are to be discouraged, as tending to draw off to America all the wealth of Europe.
|THE PHYSIOLOGICAL POSITION OF TOBACCO.|
IN speaking of the physiological position of tobacco, we have to deal with the action of the essential principles of that plant upon the human system. The peculiar effects of tobacco are due to the action of the essential oil of tobacco in the case of chewing and snuffing, and to that combined with the empyreumatic oil in smoking. Nicotine, as this essential principle is called, is so deadly an alkaloid, that the amount of it contained in one cigar, if extracted and administered in a pure state, would suffice to kill two men. According to the experiments of Vohl and Eulenberg, the nicotine is decomposed, in the process of smoking, into pyridine, picoline, and other poisonous alkaloids, which can also be obtained in varying quantities by the destructive distillation of other vegetable substances.
Nicotine, as for convenience we may continue to call the poisonous principles of tobacco, can enter the body through various channels by the stomach, by the lungs, by subcutaneous injection, and by the skin itself. But, in whatever manner it enters the human system, its effects are, in the main, uniform.
The most immediately noticeable symptom following smoking is the