1G2 History of Mechanical Inventions and 



Having taken the outline of the original design upon transparent paper, 

 by tracing all the lines of the original with a dry point, more or less fine, 

 the outline is then glued by its edges upon a board, and there is spread 

 over it with a piece of fine linen, a sufficiently hard paste, formed with 

 lithographic ink dissolved in essence of turpentine, which may be made in 

 a spoon, exposed to the heat of a candle. The outline is then rubbed hard 

 with a pitce of clean linen, till the linen ceases to have a black tint. The 

 outline is then transferred to the stone by means of a press. For this pur- 

 pose M. Laurent places in a vertical paper press the stone and the outline 

 in contact, taking care to place above the latter from twenty to twenty-five 

 sheets of paper wetted in water, and adding in solution some calcined mu- 

 riate o£ lime. Upon these last sheets is put a stone, and to prevent any 

 injury, two large plates of paper about an inch thick are interposed. The 

 pressure is then applied for an hour, and upon separating the stones it will 

 be found that-the transparent outline adheres more or less to the stone. 

 The paper is then removed by hot water, and the design is left upon the 

 stone, which is now washed with cold water till no trace of the transparent 

 paper remains. There is no fear of the outline dissolving, as the base of 

 the muriate of lime forms with the oil of the soap an insoluble soap, while 

 the soda is combined with the hydrochloric acid, and composes a soluble 

 salt, which has been carried away by the washing. 



MM. Thenard and Blainville, who commend highly this process, pro- 

 pose the following lithographic ink as superior to any other, viz. soap one- 

 fourth, mutton suet one-half, yellow wax one part, mastic in tears one- 

 half, and as much lamp black as is necessary. The whole being melted 

 on a gentle fire, and well mixed, is reduced to the consistency of a 

 thick cream, by mixing with it equal parts of turpentine and lavender. 

 The commissioners also recommend a thick and strait plank in place of the 

 second stone, and they regard the process as a very valuable one in the arts. 

 — Abstract from the Ann. de Chim. September 1826, torn, xxxiii. p. 89-93. 



2. Experiments on the Discharge of Air by different Orifices. 



M. D'Aubuisson was recently led to make some interesting experiments 

 on the discharge of air by orifices of different forms, on the occasion of his 

 establishing a ventilator at the mines of Rancie (Arriege.) 



The gasometer which he used was 0.65 metres in diameter, and 0.80 high. 

 It carried a water manometer. At an aperture in the upper he put on nineteen 

 different orifices. By means of weights by which the gasometer was load- 

 ed, he caused it to descend more or less quickly. These weights brought 

 the manometer from 0.028 to 0.144 above zero, and consequently they im- 

 pressed on the current of air, which issued from the orifices, velocities of 

 from twenty-one to forty-eight metres. 



The section of the gasometer, 0.331 square metres, multiplied by the 

 height which this instrument descended in unity of time, gave the real 

 discharge. The theoretical discharge is obtained by the following for- 

 mula : 



q2 /1+0.004* 

 +/■ 13.6 b + h 



