102 ANNUAL OF SCIENTIFIC DISCOVERY. 



way interfering with the free rotation of the wheels, as the friction 

 brakes of necessity do. The lower portion of the wheel, for the time 

 being, is in exactly the same condition as a bar of soft iron placed 

 within a coil of wire circulating electricity. But as it rises up out of 

 the coil during the rotation of the wheel, it grows less and less mag- 

 netic, the descending portions of the opposite side of the circumference 

 acquiring increased magnetic power in like degree. 



Experiments, made with a large locomotive, give the following re- 

 sults : " The rapidity of rotation, however great it may be, does not 

 at all effect the process of magnetizing the wheels. This is conceiv- 

 able, when we reflect upon the rapidity of the propagation of electricity, 

 and upon the instantaneousness of the magnetizing action. 



" Upon a horizontal plane of iron, dry and perfectly polished, the 

 force required to make an electro-magnet slide is, clearly, to the force 

 required to remove it vertically from the plane, as the force required 

 to make a mass of unmagnetized iron slide to' the weight of that 

 mass. 



" But this is not the case upon inclined planes. While the co- 

 efficient of the force required to make the mass of iron slide, diminishes 

 till it becomes nothing, the magnetic adhesiveness remains invariable. 

 This is conceivable, since the resultant of the actions produced by a 

 magnet upon a plane of iron is perpendicular to that plane, while the 

 mass of iron, which only acts by its own weight, exercises its action 

 in the direction of the weight. 



" Thus, upon inclined railways, one portion of the surcharge in- 

 tended to produce adhesion is not only inefficient for this purpose, but 

 it even operates unfavorably, in that, by the influence of weight, it tends 

 to cause the train to descend ; while, on the contrary, magnetic adhe- 

 siveness is always the same, whatever be the degree of inclination. 

 Atmospheric perturbations, fogs, &c., which so considerably impair 

 adhesion produced by weight, do not sensibly affect magnetic adhesion, 

 which remains the same whether the rails be wet or dry. Finally, a 

 locomotive with magnetized wheels does not require a greater force of 

 traction than one of which the wheels are in the normal state." 



THOUGHTS ON TELEGRAPHIC COMMUNICATIONS TWENTY YEARS AGO. 



IN 1833, Hon. John Pickering, since deceased, by request of the 

 Boston Marine Society, delivered a lecture on the subject of " Tele- 

 graphic Language," tracing the art from the first communications 

 made by torches at the siege of Troy, until the date of the address. 

 In conclusion, he makes the following curious reflections and sug- 

 gestions, which all must acknowledge to border very closely upon the 

 prophetic : 



" But the application of the art to other subjects will naturally fol- 

 low the progress of those rapid improvements which are believed to be 

 characteristics of the present age. If, for instance, we take the case 

 of commercial affairs in general, we know what a change has taken 

 place in the transmission of intelligence, relating to business, within 

 a few years past ; and it would seem, too, as if every new impulse in 



