March 6, 1890] 



NATURE 



423 



shells of the Upper Silurian rocks may be detected in the 

 Lower Silurian, the mass of organic remains in each 

 i^roup is very distinct." Later he makes the number of 

 identical species larger ; but even the newest results do 

 not increase it so far as to set aside Murchison's general 

 statement of 1838. 



Sedgwick, with all the light which the fossils of the 

 " Silurian System " were calculated to throw on his 

 Upper Cambrian series, found in the work no encroach- 

 ments on his field or on his views. They were still side 

 by side in their labours among the hitherto unfathomed 

 British Palaeozoic rocks. 



In 1840 and 1841, Murchison was in Russia with M. de 

 Verneuil and Count Keyserling, and also in Scandinavia 

 and Bohemia, seeking to extend his knowledge of the 

 older fossiliferous rocks and verify his conclusions ; and 

 in 1845 the great work on the " Geology of Russia and 

 the Urals" came out, with a further display of Upper and 

 Lower Silurian life. In his Presidential addresses of 

 1842 and 1843, reviewing the facts in the light of his new 

 observations, he went so far as to say that the Lower 

 vSilurian rocks were the oldest of fossiliferous rocks, and 

 that the fossiliferous series of North Wales seemed to 

 exhibit no vestiges of animal life different from those of 

 the Lower Silurian group. 



Still Sedgwick made no protest. He states definitely 

 on this point in his paper of 1852 (O. J. Geol. Soc, viii. 

 153, 1852), that from 1834, the time of the excursion with 

 Murchison, until 1842, he had accepted Murchison's con- 

 clusions, including the reference of the Meifod beds to 

 the Caradoc or Silurian, without questioning ; but that 

 from that time, 1842, he began to lose his confidence in 

 the stability of the base-line of the " Silurian System." 

 He adds that in 1842, Mr. Salter, the palaeontologist, in- 

 formed him that the Meifod beds were on the same 

 horizon nearly with the Bala beds ; and he accepted this 

 conclusion to its full extent, using the words, " if the 

 Meifod beds were Caradoc, the Bala beds must also be 

 Caradoc or very nearly on its parallel." Thus the infer- 

 ence of Murchison was adopted, and discrepancy between 

 them deferred. And on the following page he acknow- 

 ledges that all his papers of which there is any notice in 

 the Proceedings or Journal of the Geological Society 

 between 1843 and 1846 admit this view as to the Bala 

 beds and certain consequences of it — "mistakes,'' as he 

 pronounced them six years later, in 1852 (Q.J. Geol. Soc, 

 viii. 154, 1852). 



In 1843, Sedgwick read before the Geological Society 

 in June, a paper entitled "An Outline of the Geological 

 Structure of North Wales," which was published in 

 abstract in the Proceedings (iv. 251) ; and in November 

 of the same year, one " On the Older Palaeozoic (Proto- 

 zoic) Rocks of North Wales " (from observations by him- 

 self in company with Mr. Salter), which appeared, with a 

 map, in the Journal of the Geological Society (i. i). The 

 abstract in the Proceedings was prepared by Mr. War- 

 burton, the President of the Geological Society, and the 

 paper of the following November makes no allusion to 

 this fact, or any objection to the abstract. 



A remarkable feature of the November paper is that it 

 nowhere contains the term " Upper Cambrian " or even 

 *' Cambrian," although the rocks are Sedgwick's Upper 

 Cambrian, together with Murchison's Upper Silurian. 



A second fact of historical interest is the use of the 

 term " Protozoic," not in the sense in which it was intro- 

 duced by him in 1838, but in that in which introduced in 

 1838 by Murchison, on p. 11 of his "Silurian System," 

 where he says : — 



" But the Silurian, though ancient, are not, as before 

 stated, the inost ancient fossiliferous strata. They are, in 

 truth, but the upper portion of a succession of early 

 deposits which it may hereafter be found necessary to 

 describe under one comprehensive name. For this pur- 

 pose I venture to suggest the term * Protozoic Rocks 



thereby to imply the first or lowest formations in which 

 animals or vegetables appear." 



These facts are in accordance with Sedgwick's ac- 

 knowledgment, already mentioned. 



The map accompanying the paper as originally pre- 

 pared, had colours corresponding to five sets of areas, 

 those of the " Carboniferous Limestone," " Upper Silu- 

 rian," " Protozoic Rocks," " Mica and Chlorite Slate," 

 " Porphyritic Rocks" ; and here again Cambrian, Upper 

 or Lower, does not appear, the term Protozoic being 

 substituted. The map, as it stands in the Journal of the 

 Geological Society, has, in place of simply " Protozoic,"' 

 the words " Lower Silurian (Protozoic)." Sedgwick com- 

 plains, in his paper of 1852, pp. 154, 155, of this change 

 from his manuscript, and attributes it to Mr. Warburton, 

 saying that " the map with its explanations of the colours 

 plainly shows that Mr. Warburton did not comprehend 

 the very drift and object of my paper." " I gave one 

 colour to this whole Protozoic series only because I did 

 not know how to draw a clear continuous line on the map 

 between the Upper Protozoic (or Lower Silurian) rocks 

 and the Lower Protozoic (or Lower Cambrian) rocks." 

 " Nor did I ever dream of an incorporation of all the 

 Lower Cambrian rocks in the system of Siluria." Sedg- 

 wick also says on the same point : " I used the word 

 ' Protozoic ' to prevent wrangling about the words Cam- 

 brian and Silurian." But this is language he had no 

 disposition to use in 1843, as the paper of 1843 shows. 



Page 155 has a footnote. In it the aspect of the 

 facts is greatly changed. He takes back his charges, 

 saying, " I suspect that, in the explanation of the blank 

 portion of the rough map exhibited in illustration of 

 my paper I had written ' Lower Silurian and Protozoic,' 

 and that Mr. Warburton, erroneously conceiving the 

 two terms identical, changed the words into Lower 

 Silurian (Protozoic)." " I do not by any means accuse 

 Mr, Warburton of any ititcntional injustice — quite the 

 contrary ; for I know that he gave his best efforts to the 

 abstract. But he had undertaken a task for which he 

 was not prepared, inasmuch as he had never well studied 

 any series of rocks like those described in my papers." 

 Sedgwick here uses Protozoic in the Sedgwick sense, 

 not, as above, in the Murchison sense. Sedgwick again, 

 in 1854, speaks of "the tampering with the names of my 

 reduced map." But these explanations of his should 

 take the harshness out of the sentence, as it was in 1843 

 to 1846 out of all his words. 



The paper has further interest in its long lists of fossils 

 in two tables : (I.) " Fossils of the Older Palaeozoic (Pro- 

 tozoic) Rocks in North Wales, by J. W. Salter and J. 

 de C. Sowerby," showing their distribution ; and (2) " Fos- 

 sils of the Denbigh Flagstone and Sandstone Series." 



Thus, until 1846, no serious divergence of views had 

 been noted by Sedgwick. This is manifested in his 

 paper on the " Slate-rocks of Cumberland," read before the 

 Geological Society on January 7 and 21, 1846 (Q J. Geol. 

 Soc, ii. 106, 122, 1846), which says, on the la^t page but 

 one : " Taking the whole view of the case, therefore, as 

 I know it, I would divide the older Palaeozoic rocks of 

 our island into three great groups — (3) the upper group, 

 exclusively Upper Silurian; (2) the middle group, or 

 Lower Silurian^ including Llandeilo, Caradoc, and per- 

 haps Wenlock ; (i) the first group, or Cambrian;" dif- 

 fering in this arrangement from Murchison only in the 

 suggestion about the Wenlock. The italics are his own. 

 He adds : — 



"This arrangement does no violence to the Silurian 

 system of Sir R. Murchison, but takes it up in its true 

 place ; and I think it enables us to classify the old rocks 

 in such a way as to satisfy the conditions both of the 

 fossil and physical as well as mineralogical development." 



But before the year 1846 closed, not only the overlap- 

 ping of their work was recognized, but also the conse- 

 quences ahead, and divergence of opinion began. 



