NATURAL PHILOSOPHY. 201 



form of the material ought to have some effect upon its tenacity, and also that 

 the strength of the article depended in some degree upon the process to which 

 it had been subjected. He had, for instance, found that softer substances in 

 which the outer atoms had freedom of motion, while the inner ones by the 

 pressure of those exterior were more confined, broke unequally, the inner 

 fibers, if he might so call the rows of atoms, gave way first and entirely separ- 

 ated, while the exterior fibers showed but little indications of a change of that 

 kind. If a cylindrical rod of lead, three fourths of an inch in diameter, were 

 turned down in a lathe in one part to about half an inch, and then gradually 

 broken by a force exerted in the direction of its length, it would exhibit a 

 cylindrical hollow along its axis of half an inch in length, and at least a tenth 

 of an inch in diameter. With substances of greater rigidity this effect was less 

 apparent. It existed, however, even in iron, and the interior fibers of a rod 

 of this metal might 'be entirely separated, while the outer surface presented 

 no appearance of change. From this it would appear that metals should never 

 be elongated by mere stretching, but in all cases by the process of wire-drawing 

 or rolling. A wire or bar must always be weakened by a force which per- 

 manently increases its length without at the same time compressing it. An- 

 other effect of the lateral motion of the atoms of a soft heavy body when acted 

 upon by a percussive force with a hammer of small dimensions in comparison 

 with the mass of metal, was that the interior portion of the mass acted as an 

 anvil upon which the exterior portion was expanded so as to make it separate 

 from the middle portions. Professor Henry exhibited a portion of bar origin- 

 ally four feet long, which had been hammered in that way so as to produce a 

 perforation through the whole length of its axis, rendering it a tube. This 

 fact appeared to him to be of great importance in a practical point of view, as 

 it might be connected with many of the lamentable accidents which had oc- 

 curred in the breaking of the axles of locomotive engines. These ought in all 

 cases to be formed by rolling, and not with the hammer. 



ON THE PECULIARITIES 'OF CERTAIN LOCAUTES IX CITIES. 



Most persons think that the reason why the west end of London is more 

 fashionable than the east is nothing more than the topographical figuration of 

 the capital. But the Academy of Sciences at Paris, at a recent session, pro- 

 nounced this opinion to be a delusion. In the first place, it appears that it is 

 not only at London, but at Paris, Vienna, Berlin, Turin, St. Petersburg, and 

 almost every other capital in Europe at Liege, Caen, Montpellier, Toulouse, 

 and several other large towns wherever, in fact, there are not great local 

 obstacles the tendency of the wealthier inhabitants to group themselves to 

 the west is almost as strongly marked as in the " Great Metropolis." In the 

 second place, at Pompeii and other ancient towns the same thing may be 

 noticed ; and, in the third place, where the local figuration of the town neces- 

 sitates an increase in a different direction, the moment the obstacle ceases 

 houses spread toward the west. This last fact may, it is stated, be particu- 

 larly observed at Rome, and. to a certain extent, at Edinburg. "When, then, 

 all cities and towns have their best districts in the west, it is pretty clear that 



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