186 PERIDOTITE. 



has been credited over forty years to a chemist by whom it showed on its face 

 it could not have been made, since Laugier was not in the habit of carrying 

 his percentages into the decimals, at most, beyond one place. 



This, and numerous other mistakes which have been found in the process 

 of looking up the analyses for this work, are obviously due to the neglect of 

 authors to verify the analyses which they take at second hand. The present 

 writer has no doubt that he has contributed his quota of errors also, although 

 he has endeavored to go to the fountain-head when possible ; but with the 

 accidents of twice copying and of passing the work through the press, the 

 chance for errors to creep in are great ; and they could only be entirely 

 eliminated by again searching out the scattered literature, and comparing 

 the originals with the tables in type — a labor which is impracticable at the 

 present time. 



Section VIII. — Peridotite. — Its Chemical CJiaraders. 



In the appended table of chemical analyses (Table IV.), when the variety 

 to which the meteorite belongs is known, the name of the variety is given, 

 with an asterisk prefixed to indicate that it is a meteorite. When the variety 

 is unknown, the simple designation, meteorite, is employed. The varieties of 

 the terrestrial peridotites are given so far as possible ; but when not known, 

 the term used by the analyst to designate the rock is placed in the column 

 of varieties. 



The specific gravity of the unaltered peridotites is generally between 

 3.00 and 3.80, with the meteorites standing, as a whole, somewhat higher 

 than the terrestrial forms, since they are less altered. As the alteration 

 proceeds, the percentages in general fall, as was observed in the case of 

 cumberlandite. Two of the carbonaceous meteorites fall very low on the 

 scale, being 1.7025 and 1.94. These meteorites are thought to belong to 

 this group in all respects except their carbonaceous matter, for sections of 

 the Cold-Bokkeveld meteorite are seen as dense black masses, with brownish- 

 gray spots of silicates and carbonaceous grains. The whole mass is very 

 friable, and the silicates are in minute grains ; but they appear to be chiefly, 

 if not entirely, olivine and enstatite. The resemblance to a mass of mixed 

 soot and olivine grains is striking — the latter being seen scattered here and 

 there through the dark mass. 



To return : the specific gravity of the altered forms, particularly of 



I 



