198 Miscellaneous Intelligence. 



4. Discovery of Rocks under the Surface of the Sea. — ^The fishers 

 of the Mcditerrnneaii use an apparatus for the discovery of rocks 

 beneath the surface in those places where they wish to cast their 

 nets, which suppHes, in a great measure, the insufficiencies of the 

 ordinary means of taking soundings. The method consists in 

 carrying a long and thin cord over the bottom to be examined, and 

 which, when it meets with an obstacle, is stopped by it and becomes 

 folded in the place where it occurs. It will easily be understood, 

 that when a cord has been carried over a certain space without 

 meeting with any resistance, that proof is obtained of the non-exist- 

 ence of rocks or other obstacles, at a depth less than that to which 

 the cord has been sunk ; and as the examination can easily be car- 

 ried on to 100 feet below the surface, it may be said that, wherever 

 such an apparatus has passed unimpeded, the navigation is free. 

 If, on the contirary, some isolated rocks are found during the exa- 

 mination, the place where the cord becomes doubled points out the 

 locality, which may then be determined more accurately by other 

 trials, and the summit and neighbourhood of the submersed rocks be 

 accurately examined by means of sonndings.^^ Ann^ales Marit.; 

 Bull. Univ. F. viii. 44. 



5. Paper to resist Humidity. — This process, which Is^flttft tb 

 M. Engle, consists in plunging unsized paper once or twice into a 

 clear solution of mastic in oil of turpentine, and drying it by a 

 gentle heat. The paper, without becoming transparent, has all the 

 properties of writing-paper, and may be used for the same purposes. 

 It is especially recommended for passports, workmen's books, legal 

 papers, &c. When preserved for years it is free from injury, either 

 by humidity, mice, or insects. It is further added, that a solution 

 of caoutchouc will produce even a still better effect. — Kunst und 

 Gewerbe-hlatte. 



6. Professor Amides Microscopes. — This distinguished personage 

 has lately exhibited to the savans of this country two microscopes 

 of his own workmanship, — an achromatic refractor, and a reflector 

 of his own particular invention. The object-glass of his refractor 

 is of a very complicated construction, and is composed of three 

 double-object glasses combined together in the space of about au 

 inch. The flint-glass from which his concaves are formed is of the 

 manufacture of Frauenhofer; his convexes are of Dutch plate, 

 crown-glass, and French plate, separately. Each object-glass 

 detached has but a small aperture, and is of long focus ; but when 

 the three are combined together, the angle of aperture is very 

 considerable, and the focus short. By this ingenious arrangement 

 the trouble and difficulty of manipulating deep single-object-glasses 

 of large aperture is avoided ; but advantages gained one way, in 

 practical optics, are generally lost in another, and the twelve sur- 

 faces of the objective produce a kind of soilness and muddiness in 



