610 Foreign and Miscellaneous Intelligence. 



it was found that a greater electro-magnetic effect was produced 

 with a long copper wire than with a short one, for when the ends of 

 the battery were connected with the coil surrounding a small horse- 

 shoe magnet, it raised only seven ounces ; but when one-fifth of a 

 mile of copper-wire was interposed, it raised eight ounces. The 

 author gives his opinion of the cause of this remarkable effect in the 

 form of a query. ' On a little consideration, however, the above 

 result does not appear so extraordinary as at first sight, since a 

 current from a trough possesses more projectile force, to use Pro- 

 fessor Hare's expression, and approximates somewhat in intensity 

 to the electricity from the common machine. May it not also be a 

 fact, that the galvanic fluid, in order to produce the greatest mag- 

 netic effect, should move with a small velocity, and that, in passing 

 through one-fifth of a mile, its velocity is so retarded as to produce a 

 greater magnetic action V 



Dr. Ten Eyck varied these experiments, so as to get a small tem- 

 porary magnet which should raise the greatest number of times its 

 own weight. With a small horseshoe of round iron slightly flat- 

 tened, one inch in length, and T 6 ff inch in diameter, and wound with 

 three feet of brass wire, it raised, by means of the cylindrical battery, 

 420 times its own weight. The author remarks, ' the strongest mag- 

 net we can find described, is one worn by Sir Isaac Newton in a ring, 

 weighing three grains; it is said to have raised 746 grains, or 250 

 times its own weight.' Hence it is evident that a much greater 

 degree of magnetism can be developed in soft iron by a galvanic 

 current, than in steel, by the ordinary method of touching *. 



15. ON THE INTENSITY OF THE EARTH'S MAGNETISM. (Kvpjfer.*) 



i. During a scientific journey in the neighbourhood of Mount 

 Elbrouz, undertaken by the Academy of Sciences at St. Petersburg!!, 

 M. Kupffer and M. Lenz made a series of important magnetical 

 observations, of which we shall give a short abstract. 



Observations had frequently been made at different elevations 

 above the surface of the sea, and nearly at the same place, on the 

 intensity of the earth's magnetism ; but, contrary to what might be 

 expected, no diminution of intensity had been observed in rising 

 above the level of the sea. MM. Gay-Lussac and Biot, during their 

 aerial ascent, had made the same needle oscillate at the surface 

 of the earth, and at the height of 6000 metres, without observing 

 any diminution in the time of an oscillation. Hence it was con- 

 cluded that no sensible diminution of the intensity of the earth's mag- 

 netism had taken place at that elevation. In this conclusion, an 

 element, which has considerable effect on the magnetism of the 

 needle itself, namely, temperature, was entirely overlooked. The 

 effect of temperature on the magnetism of needles has been carefully 

 observed by M. Kupffer, and entered as an element in the data 

 from which the intensity of the earth's magnetism was deduced. 



* Silliman's Journal. See our account of Professor Moll's experiments, at 

 page 379 of this volume. 



