11G ANNUAL OF SCIENTIFIC DISCOVERY. 



ON TOE FORMATION OF FULGURITES. 



In June ISoO, a violent thunder-storm occurred at Oldenburg, Germany. 

 On the Haute liiver, four workmen were on board a dredging-boat, occupied 

 in deepening the new bed for the river, when all at once the lightning struck 

 the shore close to them ; they appeared at the same instant to be struck 

 violently on the head with a soft body. Having recovered from the shock, 

 they perceived smoke rising from a point of the shore; they ran to the place, 

 and in the burnt grass they discovered, about seven yards from the water, 

 two holes near one another, and their edges surrounded with a whitish sand. 

 They dug carefully, and found in each hole a tube, that they were unable to 

 extract entire, on account of its fragility; but they followed them as far as 

 the marshy soil situated under the 'sand. These were two fulgurites, having 

 the ordinary appearance, being round and as thin as sheets of paper, per- 

 fectly enamelled on the inside, but garnished on the exterior with grains of 

 sand; there were also, here and there on the outside, spots of green oxide 

 of iron, of the color of bottle-glass. The soil was formed of about three 

 inches of vegetable earth on the surface, then came twenty inches of white 

 sand, and lastly the boggy earth. The fulgurite began and ended at the 

 superior and inferior surfaces of the bed of sand. The principal fragments 

 have been placed in the museum of Oldenburg. 



NEW ELECTRIC LIGHT. 



Galignani's Messenger thus describes a new apparatus for producing an 

 electric light, recently exhibited in Paris : "The principle on which it is con- 

 structed is electro-magnetism; that is, the property which electricity has, un- 

 der certain circumstances, of producing magnetism inversely and conversely. 

 Suppose a wire, many yards in length, and covered with silk, to be coiled 

 round a hollow cylinder, and let a magnetic bar of steel fit like a core in 

 the hollow; then, each time the core is introduced into the cylinder, an 

 electric current passes through the wire; and though of short duration, its 

 intensity is proportional to the length of the coil. Again, each time the 

 core is taken out, another electric current is produced in an inverse direction ; 

 so that by constantly inserting and drawing out the core, an indefinite num- 

 ber of electric currents may be obtained. If the core, instead of being a 

 magnetic steel bar, consists of a bar of unmagnetized iron, and an electric 

 current be made to pass through the coil of wire, then an equally singular 

 effect is obtained; the iron core becomes so highly magnetized, that it will 

 raise heavy bars of iron, and the attraction is so great that it requires a 

 strong man to wrench the bar from the magnetized core. The effect, IIOAV- 

 ever, ceases as soon as the electric current is interrupted. It i3 clear, from 

 this, that it is much easier to obtain a permanent effect by magnetizing and 

 uiimagnctizing in this way, than by alternately inserting and withdrawing 

 out a steel magnet, as in the former method. And the only difficulty that 

 remains is to giA*e the apparatus a convenient mechanical arrangement. 

 This is done as follows : suppose a hexagonal frame placed horizontally on 

 legs, like a table. At each of the angles let there be one of the electro- 

 magnets, or cylinders of induction, with wire coiled round, as above described, 

 and supported by an inner frame, so that the whole may have the appear- 

 ance of a horizontal wheel, with electro-magnets for spokes; only the nave 

 is supplied by a hollow frame. In this hollow there fits a drum, revolving 



