92 



SCIENCE 



[N. S. Vol. XXVIII. No. 707 



other social circles the type may appear thus. 

 " There is a lady medium in Omaha who is the 

 wife of a prominent citizen. She is afflicted, 

 being nearly blind. This lady, in her 

 seances, produces large quantities of cut 

 flowers, which she claims to materialize from 

 their ' astral forms.' Most persons would 

 think that a lady of her standing, and 

 afflicted in the manner she is, would not de- 

 ceive." The flowers are real flowers, and the 

 medium allows ladies to examine her clothing 

 to see that no flowers are concealed about her 

 person. Yet no one pays attention to a con- 

 federate under whose ample skirts the 

 " astral " flowers take shelter until needed, 

 nor is the public aware of regular consign- 

 ments of flowers to the medium from " a 

 greenhouse in Council Bluffs." As to the 

 psychology of the sitters, it is doubtless com- 

 plex and divisible into many types. In the 

 main it is not the performance that convinces 

 against protest and despite intellectual an- 

 tagonism; but rather that prepossession finds 

 support in seeming mystery and flies to evils 

 that it knows not of. The most common 

 trait is the assurance that in the case observed 

 there really was no room for trickery or 

 malobservation. Why such assurance should 

 be so common a trait it is not easy to explain. 

 One wishes for such persons the attitude at- 

 tributed (possibly without due warrant) to Sir 

 Walter Scott: when asked whether he be- 

 lieved in ghosts, he is said to have replied, 

 " No ! I have seen too many of them." 



J. J. 



A UNIQUE COLLECTION OF PERIDOTITE 

 State Mineralogist J. F. Whitlaok, of 

 Little Eock, Ark., has recently arranged and 

 placed on exhibition at the Bureau of Mines, 

 Manufactures and Agriculture, a unique col- 

 lection of peridotite which is attracting much 

 attention. 



The collection contains specimens of the 

 peculiar peridotite breccia from the three well- 

 known American localities, those of Arkansas, 

 Kentucky and New York, arranged side by 

 side with similar rock and concentrates from 

 the most noted of the African mines, indi- 

 cating more forcibly than could a lengthy 



description the extremely close resemblance 

 between the rocks of these widely separated 

 localities. So close is the resemblance be- 

 tween the peridotites from these various locali- 

 ties, as shown by the specimens both rough 

 and polished, that it is almost impossible to 

 distinguish between them. 



The rock is a dark green, almost black, 

 porphyritic mass composed largely of grains 

 and crystals of olivene. The tendency of this 

 mineral to alteration is well known, and 

 specimens of the alteration products — the 

 green and yellow serpentinous earths from the 

 various localities — are also shown. These 

 earthy products are interesting economically 

 as well as scientifically, for it is by washing 

 and screening them that the heavy concen- 

 trates are obtained from which the diamond 

 and other gems are subsequently sorted. The 

 collection thus shows the various stages 

 through which the rock passes from practically 

 the fresh unweathered condition through the 

 partly altered peridotites into the softer green 

 and yellow earths to the concentrate of pebbles 

 and gems. Besides the much prized diamond 

 the latter includes the light green olivene, 

 bright red garnet and deep blue diopside crys- 

 tals. The last named has not as yet been 

 recognized in the Arkansas deposits. 



To the scientist the problem of explaining 

 how these gems come to be locked up in this 

 peculiar volcanic material is of greater in- 

 terest than the question of securing them, and 

 it is hoped that a study of the conditions at 

 some of these localities may explain the per- 

 plexing problem. At several of the occur- 

 rences the diamondiferous peridotite pene- 

 trates beds of shales rich in carbon, hence it 

 has been suggested that the diamond, which 

 is merely crystallized carbon, owes its presence 

 to the fact that the heated material forced its 

 way as a partially liquid mass through the 

 adjoining carbon-bearing shales, absorbing 

 some of their carbon which later crystallized 

 from the cooling magma as the diamond. 

 This plausible hypothesis would no doubt still 

 be regarded as the true explanation were it 

 not for the fact that at several of the diamond 

 mines no carbon shales are known, hence the 

 diamond could not have been derived from 



