522 



brought before the notice of geologists by Dr. Dawson, in a letter dated 

 March 28th, 1866,* the case was announced to be an example of 

 " Eozoon preserved simply in carbonate of lime, without any serpentine 

 or other foreign mineral ;" and a " conclusive answer to" our " objec- 

 tions." Now, what proofs have come to light to warrant this expres- 

 sion ? In a " Note on supposed Burrows of Worms in the Laurentian 

 Rocks of Canada," subsequently read (June 20, 1866,) before the Geo- 

 logical Society, nothing more appears with reference to the case than an 

 allusion merely to " fragments of 'JSozoon, not fossilizedby serpentine, but 

 simply by carbonate of lime !"f While in the brief and only other account 

 publishedof it by Dr. Dawson, and written about twelve months after the 

 announcement was made, the infilling is ignored altogether ! J Dr. Carpen- 

 ter, it is true, mentions something additional on this point; but he merely 

 makes the statement, unsupported by any proper evidence, " that the 

 canals, being filled with a material either identical with or very similar 

 to that of the substance" (" crystalline dolomite," Dawson) " in which 

 they are excavated, are so transparent as only to be brought into view 

 by careful management of the light. "§ Considering that our "ela- 

 borate arguments had at one time a strong show of support" (War- 

 rington W. Smith) — is this all that is required to prove that the 

 canals are filled with " carbonate of lime pure and simple?" Must 

 the Madoc specimen, now, be considered " to close the discussion ?" Sup- 

 posing the " transparent material" to be a carbonate, which is not at 

 all made clear, it may still be assumed that the " very characteristic 

 examples of the canal system" are of purely mineral origin. The 

 substance in which they are " excavated," according to Dawson, is 

 "crystalline dolomite"— a matrix rarely free from some imbedded 

 crystalline or other configurations. In our former communication we 

 showed that the dolomitic rocks of the North of England are often charged 

 with cylindrical coralloidal or dendritic shapes, composed of carbonate of 

 Ume:\\ if these were on a small scale, many of them would closely resem- 

 ble the " various forms of the canal system" observed in the " fragment" 

 from Madoc. Most of the limestones occurring in the latter place are 

 siliceous dolomities, and contain more or less carbonate of iron : as 

 such, they are likely to hold configurations of a " transparent material," 

 possibly a ferriferous calcite, or other mineral carbonate, which, with- 

 out proper testing, might be considered as " either identical with or 

 very similar to, that" of their imbedding substance. 



But another case, similarly interpreted, has also turned up. Dr. 

 Carpenter has detected in "sections of a specimen of Eozoon' 1 

 dendritic and other forms of the "canal system," which, as they 

 agree closely in transparency and colour with their enclosing calcite 



* " Quarterly Journal of Geological Society," vol. xxii., p. 228. 

 f " Quarterly Journal of Geological Society," vol. xxii., p. 609. 

 % "Quarterly Journal of Geological Society," vol. xxiii.', p. 261. 

 § "Quarterly Journal of Geological Society," vol. xxii., p. 212. 

 || " Geology of Canada," 1863, pp. 592, 593. 



