walcott.] NOMENCLATURE CAMBRIAN. 237 



This method necessitates the multiplication of names,but if it insures 

 accuracy of statement and meaning it is much better than the use of a 

 *ew old names that have been established in some one geologic province 

 and extended over other upper Cambrian formations in other geologic 

 provinces that cau not be proved to be identical or synchronous. 



(/) The study of the serial relations among rocks by the modern 

 method is of as much importance as that of the specific relations of dis- 

 tinct horizons or of particular formations. The serial relations of one 

 series of rocks in one province can be compared with the serial relations of 

 another group in another province ; but the two should receive separate 

 names and be grouped uuder the greater series to which they belong. 

 For instance, the Trenton series of New York may be compared with 

 the Lebanon series of Tennessee and united as a portion of the Lower 

 Silurian (Ordovician) and respectively compared with the same portion 

 of the Lower Silurian (Ordovician). 



(g) If it is found that the strata included in a named formation, ter- 

 rano, or group embraces portions of other formations, terranes, or groups 

 it is allowable to remove portions of such formations, terranes, or groups 

 and still apply the original name, if the portion remaining is distinct or 

 was first described and included uuder the name. 



(h) Geologic nomenclature should, in all its parts, be the natural 

 expression of the inter- relationships and mutual subordination of the 

 facts it is the especial aim to associate and systematize. 1 



CAMBRIAN. 



The term Cambrian was first introduced to the attention of geologists 

 at the Dublin meeting of the British Association for the Advancement 

 of Scieuce in August, 1835. A joint paper was read by Prof. Adam 

 Sedgwick and Ii. I. Murchison, entitled " On the Silurian and Cam- 

 brian Systems, exhibiting the order in which the older sedimentary 

 strata succeed each other in England and Wales." An abstract of this 

 paper appeared in the account of the proceedings of the British Asso- 

 ciation published in the Edinburgh New Philosophical Journal for 

 April-October, 1835, page 390. In this the name Cambrian is spelled 

 Cumbrian, probably by a typographical error. The paper appeared in 

 1836, in volume 5 of the Reports of the Association. In the account of 

 the Transactions of the Sections it says : 2 



Prof. Sedgwick commenced by pointing out the imperfection of the sections ex- 

 hibited in the north of England and some portions of north Wales, in consequence of 

 the entire want of continuity between the Carboniferous series and the interior schis- 

 tose group. * * * Prof. Sedgwick then described in descending order the group 

 of slate rocks as they are seen in Wales and Cumberland. To the highest he gave 

 the name of Upper Cambrian group. It occnpios the greatest part of the chain of the 

 Berwyns, where it is connected with the Llandeilo flags of the Silurian system, and 

 ■ — 



'On the tripartite classification of the Lower Paleozoic rocks ; Charles Lapworth, Geol. Mag., new 

 series, dec. II, vol. 6, 1879, p. 11. 



* Brit Assoc. Report for 1835, part 2, Trans, of Sections, 1836, p. 60. 



