396 Scientific Intelligence, [May, 



muriatic, nitric, and dilute sulphuric acids ; and from its solution in 

 muriatic and sulphuric acids, the deliquescent salt of muriate of mag- 

 nesia and regular crystals of sulphate of magnesia were obtained. On 

 some occasions, a very slight effervescence takes place ; but this no 

 doubt arises from adhering particles of carbonate of lime, or from a 

 small quantity of carbonic acid, which may have been absorbed by 

 exposure to the atmosphere. 



The following analysis of this mineral has been made by Dr. Fyfe : 



Magnesia 6975 



Water 3025 



100-00 

 (Edinburgh Philosophical Journal.) 



IV. Results of Experiments, xvith a Magnetimeter invented by Mr. 



Scoresby. 



1. Iron bars become magnetical by position, excepting when placed 

 in the plane of the magnetic equator ; the upper end, as regards the 

 position of the magnetic equator, becoming a south pole, and the 

 lower extremity a north pole. 



2. No attraction or repulsion appears between a magnetized needle 

 and iron bars; the latter being free from permanent magnetism, 

 whenever the iron is in the plane of the magnetic equator; conse- 

 quently, by measuring the angle of no-attraction in a bar placed north 

 and south, we discover the magnetic dip. 



3. Before a magnet can attract iron, that is totally free from both 

 permanent magnetism and that of position, it infuses into the iron a 

 magnetism of contrary polarity to that of the attracting pole. 



4?. A bar of soft iron held in any position, except in the plane of the 

 magnetic equator, may be rendered magnetical by a blow with a 

 hammer, or other hard substance ; in such cases, the magnetism of 

 position seems to be fixed in it so as to give it a permanent polarity. 



5. An iron bar, with permanent polarity, when placed any where in 

 the plane of the magetic equator, may be deprived of its magnetism 

 hy a blow. 



6. Iron is rendered magnetical if scowered or filed, bent or twisted, 

 when in the position of the magnetic axis, or near this position ; the 

 upper end becoming a south pole, and the lower end a north pole; 

 but the magnetism is destroyed by the same means, if the bar be held 

 in the plane of the magnetic equator. 



7. Iron heated to redness, and quenched in water, in a vertical 

 position, becomes magnetic; the upper end gaining south polarity, and 

 the lower end north. 



8. Hot iron receives, more magnetism of position than the same 

 when cold. 



9. A bar-magnet, if hammered when in a vertical position, or in the 

 position of the magnetic axis, has its power increased if the south 

 pole be upward, and loses some of its magnetism if the north end be 

 upward. 



10. A bar of soft steel, without magnetic virtue, has its magnitude 

 of position fixed in it by hammering it when in a vertical position ; and 



