OPPONENTS AND OBJECTIONS. 185 



" 4th. The ' chamber casts ' being composed occasionally of 

 loganite and malacolite, besides serpentine, is a fact which, 

 instead of favouring 1 their organic origin, as supposed, must 

 be held as a proof of their having been produced by mineral 

 agencies; inasmuch as these three silicates have a close 

 pseudomorphie relationship, and may therefore replace one 

 another in their naturally prescribed order. 



"5th. Dr. Giimbel, observing rounded, cylindrical, ortuber- 

 culated grains of coccolite and pargasite in crystalline cal- 

 careous marbles, considered them to be ' chamber casts,' or 

 of organic origin. We have shown that such grains often 

 present crystalline planes, angles, and edges ; a fact clearly 

 proving that they were originally simple or compound crystals 

 that have undergone external decretion by chemical or solvent 

 action. 



" 6th. We have adduced evidences to show that the ' nummu- 

 line layer' in its typical condition that is, consisting of 

 cylindrical aciculi, separated by interspaces filled with calcite 

 has originated directly from closely packed fibres ; these 

 from chrysotile or asbestiform serpentine; this from in- 

 cipiently fibrous serpentine ; and the latter from the same 

 mineral in its amorphous or structureless condition. 



" 7th. The ' nummuline layer,' in its typical condition, un- 

 mistakably occurs in cracks or fissures, both in Canadian and 

 Connemara ophite. 



" 8th. The ' nummuline layer ' is paralleled by the fibrous 

 coat which is occasionally present on the surface of grains of 

 chondrodite. 



" 9th. We have shown that the relative position of two super- 

 posed asbestiform layers (an upper and an under 'proper 

 wall'), and the admitted fact of their component aciculi 

 often passing continuously and without interruption from one 

 'chamber cast' to another, to the exclusion of the 'inter- 

 mediate skeleton,' are totally incompatible with the idea of 

 the 'nummuline layer' having resulted from pseudopodial 

 tubulation. 



" 10th. The so-called ' stolons ' and ' passages of communi- 

 cation exactly corresponding with those described in Cyclo~ 



