218 



SCIENCE. 



[Vol. I., No. 8. 



monthlj' wind-directions as estimated from 

 the observations of the month. This chart 

 shows high pressures over the whole coun- 

 try, with northerly and north-westerly winds, 

 the two combined producing the generall}' cold 

 weather of the month. The extremes of cold, 

 however, were not so great as is usual in Jan- 

 uarJ^ The mean lowest minimum tempera- 

 tures, from 47 stations of the signal-service in 

 the different states, is —6.8°, while the same 

 places indicate a mean greatest cold for all the 

 years of observation of —13.3°. The follow- 

 ing are exceptions: Pike's Peak, —37°, 4° 

 lower than in the same month for the lust eight 

 years ; Dubuque, lo., —26°, 2° lower ; Pioche, 

 Nev., —17°, 3° lower than before observed in 

 Nevada ; Santa Fe, N. Mex., —13°, 4° lower ; 

 and Spokane Falls, Washington Territory, 

 — 28°, 20° lower than before noted in the ter- 

 ritorj'. The lowest temperature reported from 

 auj'' station was —54°, at Elko, Nev., on the 

 morning of the 19th. The range of air-press- 

 ure was much less than during anj' January 

 for five years. 



There were sixteen storms traced within the 

 United States and Canada. The following 

 table gives the number of storms within the 

 United States in each January since 1877. 

 For the purpose of comparison, there are 

 added the mean velocitj', in miles per horn-, 

 of the storms in each month, as taken from 

 the annual reports of the chief signal-officer. 



TABLE OF JANUAitY STORMS AND THEIR MEAN 



VELOcrrY. 



The heaviest snowfall was 52 inches, at 

 Fort McDermitt, Nev. 



The total movement of the wind ranged from 

 27,561 miles, on Mount Washington, to 1,853 

 miles, at Jacksonville. 100 miles per hour, 

 and over, were reported from Mount Washing- 

 ton on the 3d (152, maximum for month), 4th, 

 12th, 18th, 20th, 21st, 24th, and 31st. 



There were ordered up 149 cautionarj^ sig- 

 nals, of which 79.9 per cent were fully justi- 

 fied. 



No marked displays of the aurora were 

 noted. Sun-spots were reported \>j Mr. D. P. 

 Todd of Amherst, Mass., as seen on 11 days. 

 The.y were least numerous at the first and last 

 of the month, with a maximum frequency 

 about the 16th. 



An earthquake-shock was felt early on the 



morning of the 11th in Nashville, Jackson, 

 Clarksville, and Memphis, Tenn. ; Paducah, 

 Ky. ; Cairo, Anna, and CoUinsville, 111. ; and 

 at St. Louis and Protem, Mo. 



A drought of great severitj'' was reported 

 from parts of Maine and Vermont. 



Among numerous other statistics, are tables 

 of monthl}^ rainfall and mean temperature at 

 Sacramento, Cal., for thirty years, — ^from 

 1853 to 1882 inclusive. 



THE GEOLOGY OF LAKE SUPERIOR. 



Me. SELWYTSf, the director of the Geological survey 

 of Canada, has given in Science for Feb. 9 (p. 11) 

 a note on the age of the rocks on the north shore of 

 Lake Superior. The uncrystalline strata of the re- 

 gion, more or less associated with igneous rocks, are, 

 as is "well known, unconformable to and distinct from 

 the Huronian. Mr. Selwyn includes them in ascend- 

 ing order in three groups, which will be found de- 

 scribed in detail in the Geology of Canada in 1863. 



1. Blackish and bluish argillites, with chert, and 

 black or dark-gray magnesian limestones and sand- 

 stones, often with magnetite, the series being gen- 

 erally colored by carbonaceous matter. 



2. Red and white sandstones and conglomerates, 

 with red, white, and mottled shales, dolomites, and 

 dolomitic marls, constituting the Nipigon group of 

 Black bay and Nipigon bay. With these he classes, 

 following Logan, the great mass of strata, including 

 melaphyres, amygdaloids, and tufas, with native cop- 

 per, — the Keweenian or cupriferous series of Michi- 

 picoton, Mamainse, and Pointe Aux Mines. 



3. The sandstones of Sault St. Mary. 



Between these three groups, according to Selwyn, 

 'there may be slight unconformities; ' but he would 

 include the whole of them in "those divisions of 

 the great lower paleozoic system which underlie the 

 Trenton group," and would call them lower Cam- 

 brian ; asserting that there "is at present no evidence 

 whatever of their holding any other place in the 

 geological series," and "no sufficient reason for in- 

 venting or adopting new and unknown names for 

 them." 



These conclusions, it should be noticed, are arrived 

 at after a first visit of a few weeks to certain parts of 

 a vast, new, and peculiar region, which has engaged 

 the attention, during the past forty years, of many 

 skilled observers, who have collected, with regard 

 to the whole of the Lake Superior basin, a great body 

 of facts, and have reached conclusions with which 

 Mr. Selwyn would seem to be wholly unacquainted. 

 The problems i^reseuted by the rocks in question 

 are far from being as simple as he supposes. 



Mr. Selwyn includes in his second division both 

 the Nipigon group of Bell and Hunt, and the Kewee- 

 nian or cupriferous series, of which he conceives the 

 third division, or St. Mary sandstone, "may be only 

 the upper part, without any intermingling of volcanic 

 material." This view of the continuity of the cu- 

 priferous series with the Potsdam (St. Mary) sand- 

 stone was maintained by Whitney; but Logan, in 

 1863, put forth strong, and to most minds conclu- 

 sive, reasons for believing that the highly inclined 

 cupriferous rocks at the east end of the lake pass 

 unconformably below this sandstone [Geol. Canada, 

 p. 85; also Geol. report Canada for 1866-69, p. 474). 

 His conclusions have since been confirmed by other 

 observers, notably by Strong and Irving in Wisconsin, 



