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that the action of the fire had rendered the fibre so brittle that 

 its tenacity was almost entirely destroyed, and the mitten was of 

 no further use. In order to explain then the seeming inconsistency 

 between the two cases, it may be stated that what is known as th e 

 Quebec asbestus of commerce, and the true asbestus, are two distinct 

 substances, and belong to two distinct groups of minerals. Thus 

 asbestus proper belongs to what is known as the pyroxene or horn- 

 blende group, while that obtained from the Quebec mines belongs 

 to the talc or serpentine group. The former is classed among the- 

 igneous rocks proper, such as syenites, granites, syenites, porphyries, 

 etc., and embraces among other varieties augite, diallage, hornblende, 

 etc. Some asbestiform minerals are augitic, but the greater number 

 belong to the hornblende family, and are known by several names,, 

 such as amianthus, asbestus, byssolite, tremolite, actinolite. In the 

 variety known as pilolite, which is also a division of the hornblende 

 group, several curious forms of asbestus occur, such as mountain paper 

 and mountain leather, in which the fibres have become felted together 

 in a somewhat uniform consistency, and are in the form of thin sheets ; 

 mountain or rock cork, which is a more massive form, and in which the 

 specific gravity ranges from .68 to 1.34, and mountain wood, the name 

 of which is derivable from its ligniform or woody aspect. The chemi- 

 cal composition of these several asbestiform minerals varies con- 

 siderably, but for the most part they may be classed as silicates of 

 alumina and magnesia, with varying proportions of lime and iron and 

 occasionally a little water. The varieties known as mountain cork and 

 leather contain a considerable proportion of water, amounting some 

 times to 23 per cen r . 



A peculiar bluish variety known as crocidolite, and found in 

 South Africa, Norway, and at several other points, contains a very 

 considerable proportion of iron protoxide, sometimes as much as 35 per 

 cent., in addition to silica, magnesia, and soda, and contains also 

 a small percentage of water. This mineral is more properly a silicate 

 of iron, and has great tensile strength as compared with the ordinary, 

 form of asbestus, though deficient in fire-resisting properties. 



These minerals occur for the most part in serpentinous rocks in the 

 oldest formations. In Canada, the variety known as actinolite occurs 



