Magnetism by Voltaic Electricity. 283 



the coal which alternate with this sand stone. If the coal 

 formation, exists as a portion of the old red sand stone, we 

 can entertain no reasonable doubt that the old red sand 

 stone itself was formed after the earth was covered with wood, 

 and if it turn out to be true, as there is some reason for be- 

 lieving that the transition and some of the primitive rocksj 

 alternate v/ith the old red sandstone, we must conclude that 

 these rocks also have been formed after the earth was cov- 

 ered with wood. — Thomson^s Annals, J\^ov. 1821. 



42. Spontaneous Combustion. 



A barrel of oat-meal which had been left in a recess of 

 the chimney of a house in Glasgow, took fire while the fam- 

 ily were absent at bathing quarters last summer. Nothing 

 remained but the iron hoops of the barrel and a few pieces 

 of charcoal. The meal was probably a little moist. — Idem. 



43. Magnetism produced by Voltaic Electricity. 



A new and interesting discovery has been made in relation 

 to the connexion between Voltaic electricity and Galvanism. 

 It has been ascertained that theVoltaic (Galvanic) fluid, direc- 

 ted in a proper manner, is capable of communicating magnetic 

 properties to bars of steel. If steel bars or rods be exposed to 

 the Galvanic current, placed in the direction of the magnetic 

 axis, no effect follows ; but if they be placed parallel with the 

 magnetic equator, they become magnetic, the end placed to 

 the west becoming the north pole of the new magnet, and 

 that toward the east the south pole. The galvanic influence 

 is so great in this respect as to exert its power at a distance 

 of some inches (even ten or twelve) so that if the steel bar 

 be moved in a circle round the course of the galvanic curv 

 rent, but always kept parallel to the magnetic equator it be- 

 comes magnetic. 



When an electrical or a voltaic battery of considerable 

 quantity is charged, the compensating or discharging wire 

 becomes magnetic upon the completion of the discharge. 

 Common needles or bars of steel placed transversely on the 

 wire, or under it, or on its sides, become permanent magnets 

 on the discharge. * 



