549 



bundles of radiating crystals, also groups of vermicular branching forms 

 (" canals and tubuli") : the " nummuline layer" is not well developed, 

 being often represented by minute radiating aciculi. We have carefully 

 tested the Chelmsford specimens, both by chemical reactions and pola- 

 rized light, without, however, detecting any evidence of the "canal 

 system" being else than siliceous; or of being composed of a substance 

 identical with or related to its calcareous matrix.* Now, we cannot 

 dispute the statement of Dr. Sterry Hunt ; as probably some mistake 

 may have been made in our specimens. "We must, however, in this case 

 too, complain of the very meagre and unsatisfactory account given of the 

 " canals and tubuli" in the otherwise more detailed notice of the Chelms- 

 ford " Eozoon," published in " Silliman's Journal," p. 77, of January last. 

 No evidence whatever is offered to show by what process the chemical 

 nature of these parts was determined; — whether the conclusion that they 

 are of the same composition as the " calcareous skeleton" was based on 

 an examination by polarized light ; or whether they do not consist of some 

 soluble silica, or of a mixture of a carbonate and a silicate such as would 

 be quite as readily acted upon by weak acid as their imbedding substance, 

 especially if it be dolomite. We wish to call particular attention to the 

 last point, as brief mention has already been made of a specimen of ela> 

 olite (a translucent variety, from Brevig), which, in consequence of its 

 being an alkaliferous silicate of alumina (and there is no reason why 

 such a compound may not occur in theLaurentian metamorphic marbles), 

 was dissolved in weak acid. Another specimen, which we have lately 

 subjected to the same process, was taken out of the solution in a partially 

 digested state. When examined with the microscope, the residuum, 

 which is in a slightly coherent condition, was found to consist of inter- 

 lacing configurations, some of which, where well separated from the rest, 

 bore no inconsiderable resemblance to the ' ' canal system" — not, it is true, 

 in its beautiful arborescent forms, but in the small crooked branching 

 varieties, common to many Canadian examples. Prismatic cleavage, 

 which elaeolite eminently possesses, had evidently favoured the develop- 

 ment of the configurations. They are transparent, rudely branching 

 and anastomosing, showing rarely any cleavage edges or planes ; these for 

 the most part having been removed by the action of the acid. 



Such a case as this clearly necessitates every point being duly con- 

 sidered before any conclusion can be drawn as to the chemical nature 

 of the " canals and tubuli," should they appear not to have their ordi- 

 nary composition. It also strikingly illustrates the view we have taken 

 that these parts in typical " Eozoon" are merely the skeletons of frag- 

 ments, or of crystals — respectively of serpentine or some other silicate — 

 which remain after their waste had been arrested through changed con- 

 ditions. Moreover, it testifies to our having succeeded in forming from 

 elseolite, by the action of a weak solvent, configurations approximating 

 to the rude varieties of the " canal system." 



* We expect still to receive specimens, undoubtedly identical with those described by 

 Dr. Sterry Hunt ; when we hope to announce with more certainty the result of our inves- 

 tigations. 



