156 Progress of Invention. 



found impossible to get rid of. Among these is a great friction be- 

 tween the piston and the barrel, and, worse still, the disarrangement 

 of the valves, on account of the oil used for lubrication getting into 

 them. M. Deleuil believes that he has avoided these, in a new form 

 of pump, which will answer at least for those industrial purposes in 

 which only a moderate vacuum is required. Strictly speaking, it is 

 but a modification of the hydraulic pump, to which we have already 

 directed the attention of our readers.* The piston, which so nearly 

 fills the barrel that only a sheet of paper can be inserted between 

 them, is of a length equal to twice its diameter, and has grooves on 

 its surface distant from each other about four- tenths of an inch. 

 When this piston is moved backwards and forwards in the barrel, 

 even with moderate rapidity, a vacuum equal to from three to seven 

 inches of mercury is produced in a comparatively short space of time. 

 As the air drawn from one direction may be forced onwards in the 

 opposite, the apparatus may be used as a condensing pump, so as to 

 produce a pressure of about two atmospheres. 



New and Simple Mode of Reproducing Drawings, etc. — The 

 drawing having been made with a solution of gum, glue, varnish, 

 or any other fluid which will impart hardness, it is transferred 

 to a plate of plaster of Paris, chalk, or anything else that is 

 easily pulverized. This plate, having been allowed to dry, is 

 brushed until the material between the lines of the drawing — which 

 is not affected by the process — is removed to a sufficient depth : 

 after which it is immersed in gum, or glue, to harden the entire 

 surface. The result is an admirable copy of the drawing in relief, 

 and from this a fac simile in metal may be obtained in the 

 usual way. 



Miscellaneous. — Photography in the Parle. — If a sheet of paper, 

 prepared with a solution containing 400 grains of isinglass, 440 

 grains of iodide of potassium, 146 grains of bromide of potassium, 

 54 grains of chloride of sodium, and 40 ounces of water, though it is 

 not sensitive to light, is placed upon a picture, and another sheet 

 beneath it, and they are left in contact for some time in the dark, 

 the upper sheet will be found to contain a negative of the picture, 

 and the lower a positive, in which the light greens and blues will 

 be represented by white, and the reds by red. It has not yet been 



found possible to fix these. Poofs on the principle of Suspieusion 



Pridges. — M. Lehaitre, a French civil engineer, proposes to con- 

 struct roofs having a span very far greater than any hitherto 

 attempted, by supporting them with suspension cables. They will 

 have an advantage over suspension bridges, in being free from the 



injurious effects produced by varying loads. Origin of Piamonds. 



— lfc has recently been shown by Professor G. Oppert, with great 

 probability, that diamonds are the result of the decomposition of 

 vegetable matter. They often contain, on their surface, impressions 

 of grains of sand, etc., and within them, fungi, and other organic 

 bodies. This could not be the case if they were formed at a high 



* Intellectual Observed, No. ixxvii. p. 78. 



