496 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



wall or earth there was an equilibrium existing between the 

 friction of the components of the embankment and the press- 

 ure due to their weight. Boussinesq has, however, resolved 

 the problem under the supposition that the embankment of 

 earth does actually exert a pressure over and above that 

 which is exerted by the friction, and that it is only because 

 this pressure was superior to the resistance offered by the 

 wall that the overturning has been able to begin ; and he 

 has determined, in general, the laws of the pressure exerted 

 by embankments, or by any pulverulent matter in a static 

 condition, which precedes the rupture of equilibrium. In 

 his investigations he has considered all the pressure which 

 can arise from, and to a certain extent depend upon, small 

 deformations in every elastic atom, of the mass. Pulverulent 

 matter is, therefore, considered by him as another important 

 form of matter, different from gas, solid or liquid, which un- 

 der pressure evidently becomes endowed with a certain rigid- 

 ity, like solids, but which, when it ceases to be compressed, 

 becomes a fluid. Bull Acad. Boyale de JBelgique, 1875, 63. 



PRESERVATION OF HARBORS AND ROADSTEADS. 



The remarkable labors of Captain Cialdi, of the Italian 

 ISTavy, relative to the theory of the movements of the water 

 of the ocean during storms, and the effect of waves upon the 

 transportation of material, altering the character of harbors, 

 etc., having been previously noticed, we have now to record 

 the appearance of a smaller work by him on the construction 

 of the ports of the Mediterranean. In reference to Port Said, 

 situated at the northern opening of the Suez Canal, he sug- 

 gests that, instead of constructing two complete jetties, it 

 would be better to have a large trough or opening in the 

 longer one, in such a position that the currents thereby in- 

 duced shall carry away the alluvial matter, and deposit it in 

 another portion of the channel. Tessan, a member of the 

 Academy of Science at Paris, having perceived the ration- 

 ality of this suggestion, urged that it should be put to the 

 trial ; but it was not done, and already a great inconvenience 

 has been felt in the filling up of the ship channel. The en- 

 gineer in charge of the hydraulic works of the Canal Com- 

 pany proposes now to prolong his jetties, in order to regain 

 the depth of twenty-nine feet of water; but in future years 



