Polytechnic Association Proceedings. 543 



diflBculties in digging, formerly experienced by the presence of 

 water, have been obviated. A steam dredging machine, of eighteen 

 horse power, now floats in a canal of its own construction, and 

 every minute a ponderous bucket descends to the depth of twenty- 

 six feet and brings up ten bushels of the dark green sand, which, 

 by a side motion, is dropped into a railroad car on the bank. By 

 this arrangement, neither pumping nor draining is required. The 

 apparatus, guided by two men, does the work of hundreds of hands, 

 and enables tliis company to deliver the fertilizer near their pit at 

 the rate of three cents per bushel. Its average cost at various 

 points on the railroad, extending from Port Monmouth to Phila- 

 delphia, is eight cents per bushel. By means of this and other fer- 

 tilizers obtained from the ocean, the great wilderness, which 

 formerly extended from Earitan to Delaware baj^ is being rapidly 

 brought under culture, and it is safe to predict that within twenty 

 years the whole will present the appearance of a continuous garden, 

 and that it is destined to be the principal source for supplying both 

 New York and Philadelphia with fruit and vegetables. 



CHEOMATE OF DIABENZOIE. 



This compound is said to surpass the fulminate of mercury in 

 explosive force. Mr. Griess, the French patentee, makes this body 

 by mixing one equivalent of hydrochlorate of aniline with two of 

 hydrochloric acid, gradually adding to the mixture one equivalent 

 of nitrate of soda in stronsr solution. When nitroffen oras is no 

 longer evolved, the remaining diabenzole is extracted by one 

 equivalent of bi-chromate of potash in strong solution, and one of 

 hydrochloric acid, which causes a precipitation of chromate or chloro- 

 chromate of diabenzole, which must be dried with extreme caution. 



PHOTOGRAPHS. 



The portraits made by Adam Salomon are admitted to have no 

 equals in the Paris Exposition, The London Photographic JSfews 

 says the secret of his extraordinary success lies in the long exposure 

 which he gives. He uses a rather acid bath, sufficient to insure a 

 perfectly clear picture, and then gives plenty of time. His print- 

 ing is alleged to be one source of his superiority. It is suggested 

 that he uses paper the moment it is ready, carefully avoids any 

 exposure of it to light, and produces remarkable eflects by exposing 

 the print after it comes from the frame to the light for a short time, 

 protecting the face and hands, thereby obtaining a remarkable purity 

 of tone in the flesh. 



