September 21, ISSS.) 



SCIENCE. 



403 



raiiie (the immediate ' fringe ' in tlie western i)art 

 of the state excepled) was made because of certain 

 statements to tlie contrary quite recently made by a 

 distinguished authority. It was made only after a 

 thorough investigation of every locality supposed to 

 be glaciated. 



In conclusion, I may be permitted to say that 

 while, owing to the necessarily limited length of a 

 public lecture, the rocks of Philadelphia cuuUl not 

 be so fully treated of as the superficial formations, 

 this latter — and in this region more debatable — sub- 

 ject will form the topic of future lectures, which may 

 perliaps be worthy of further comment by my friendly 

 critic. Uexrv Cakvill Lewis. 



rhiladelpbia, Sept. 7, 1883. 



The pre-Cambrian rocks of Wales. 



Those who are interested i» the questions raised 

 by Dr. Henry Hicks in bis criticism of Professor 

 Geikie in Science for Aug. 10, may find it to their 

 advantage to con^ult my paper entitled 'History of 

 some pre-Cambrian rocks in Europe aud America,' 

 which appeared in the American iournat of ncience 

 for April. 1N:*0 (vol. xix. p. -itiS-SS:!). 1 had the good 

 fortune, in 187S, to spend several days with Dr. Hicks, 

 in going over the typical localities previously studied 

 by him, not only at and n^ar St. Davids in South 

 Wales, but also those of Carnarvon, Dinorwic, and 

 Anglesea, Messrs. Tosell and Tawney being our com- 

 panions, in North Wales. As a result of tliese stud- 

 ies, I am satisfied that the views of Messrs. Hicks 

 and Hughes are correct, aud their criticisms of Pro- 

 fessor Gf ikie well founded. 



The Dimetian, .alike in North and South Wales 

 and in Anglesea, has both the lithogioal characters 

 and the stratigrapbical relations of the Laurentianof 

 North Americ.1. The Arvonian corresponds in like 

 manner to the great series of liilllfjiiiilan or petrosilex 

 rocks, jaspcry and porpliyritic, whose distribution on 

 the coast of Slassacluisetts and of New Brunswick, in 

 the Blue Kidge of Pennsylvania, in Missouri, and on 

 Lake Superior, Ibave studied and elsewhere discu-ised 

 (.Second geol. surv. Fenn., rep. E, p. 189-10.5). Simi- 

 lar rocks have also been described by Irving in the 

 Baraboo river in central Wisconsin, a locality which 

 I have lately had an opportunity of examining. Tbe 

 conglomerates of Arvonian pebbles, which form the 

 basal beds of the Cambrian near Suowdon, are indis- 

 tinguishable from those found at Marbleliead and 

 elsewhere on our eastern coast, lying on or near the 

 Arvonian. 



The Pebidi.in of Hicks is our typical Huroni.an, as 

 seen in eastern Can.ida and around the lakes Huron 

 and Superior. Professor Bonney, who has lately 

 received a collection of these, is struck with their com- 

 plete resemblance to the Welsh Pebidiau which I had 

 seen and called Huronian thirteen years since. Tbe 

 succeeding gneisses and niic.vschists (upper Pebidiau 

 or Grampian of Hicks, and Caledonian of Callaway), 

 which are our Moiitalban series, are not met with in 

 Wales, but appear not only in Scotland, but, a« I have 

 pointed out, across tbe channel, in the Dublin and 

 Wicklow hills in Ireland. 



The similar succession in the Alps, I have described 

 in a late paper, of which an abstract appeared in 

 Scik>-ce for Sept. 7 (p. ;VJ2). The student who com- 

 pares the succession of stratifit-d crystalline rocks 

 alike in North America, in the British Islands, and 

 in southern Europe, can scarcely fail to recognize, in 

 their constant stratigraphical and lithologieal rela- 

 tions, something like a ' universal law.' 



T. Steruy Hunt. 



Monu-cBl, Sept. II, 1883. 



SERGEANT FINLEY'S TORNADO STUD- 

 IES. 



Report on the character of six hundred tornadoes. Pro- 

 fessional papers of the signal service. No. vii. 

 By J. P. FiNLEY, Washington, Signal service, 

 1«82. 10 p., 3 maps, 4°. 



Tornattites : Their special characteristics and dangers, 

 iiy J. P. FiNLEV. Kansas City, 1882. 30 p. 



So striking a phenomenon as a tornado, and 

 one so destructive in its effects, would natur- 

 ally- receive much attention ; jet, curiously 

 enough, the coiiijjeteut treatment which these 

 storms have received is remaikabl}' inadequate. 

 Those omniscient gentlemen, the reportets of 

 the newspapers, have written much about tor- 

 nadoes, and many columns of our summer 

 dtiilies are filled with accounts of thom ; hut, 

 aside from the books of Peltier and Rove, the 

 scientific literature is fragmentary. Half a 

 century ago, at the time of the battle between 

 Rcid, Kedticld, Piddington, Kspy, Hare, and 

 olliers, over the rotatory theory of storms, the 

 toriKido-litcrature took a considerable develop- 

 ment ; but it soon fell to small dimensions, and 

 here it has remained until quite recently. The 

 present activity in this Held is largely due to 

 the signal service, and Sergeant Finley's con- 

 tributions form an important part of the current 

 literature. 



Mr. Finley's specialty is the collection of 

 facts concerning tornadoes. He has accounts 

 of individual tornadoes in many of the annual 

 reports of the chief signal ollicer. They repre- 

 sent the facts collected by him on the field of 

 destruction itself. They are evidenth" gotten 

 together with great care ; measurements are 

 made when practicable, and explanatoiy maps 

 and sketches are numerous. His evident ob- 

 ject is to put before the reader the accurate 

 representation of what he saw, encumbered as 

 little as possible by explanatory theories. The 

 result is that his reports are interesting read- 

 ing, and atford a mine of wealth for the future 

 Kepler of tornadoes. 



Not quite so important, perhaps, from a 

 scientific point of view, btit of far tnore general 

 interest, is his report. Its principal feature is 

 the tabulation of the tornadoes discussed, with 

 headings for time, dimensions, velocity, clouds, 

 and other meteorological features. These are 

 summed up, and from the results. are drawn 

 various interesting conclusions concerning 

 maxima, minima, and averages. 



Mr. Finley's search for accounts of tornadoes 

 has been extensive ; but as he has unfortu- 

 nately given no references, we cannot tell how 

 extensive it may have been. Evidently he has 

 not gone through the Proceedings of the Amer- 



