March 16, 1883.] 



SCIENCE. 



183 



statistics of population. — Dr. H. Paasche writes 

 regarding the population of the cities of western Eu- 

 rope during the middle ages, that, even as late as the 

 seventeenth century, no regular estimates of popula- 

 tion were made. Nobody cared for statistics of this 

 sort: consequently there is a gap in our knowledge 



of economic and social life of those times, which can 

 only be filled up by reasoning from incidental items 

 in town and city records. The writer takes up the 

 history of Kostock in the fifteenth and sixteenth cen- 

 turies, and shows how this may be done. — (Jahrh. 

 nat.-skon. statist., Nov. 1.5, 1882.) D. w. E. [411 



INTELLIGENCE PROM AMERICAN SCIENTIFIC STATIONS. 



GOVBENMBNT ORGANIZATIONS. 



Coast and geodetic survey, 



Recent deep-sea soundings of unusual depth. — In 

 the prosecution of recent deep-sea soundings off the 

 West-Indian islands by the U. S. steamer ' Blake ' 

 (Lieut.-Comdr. W. H. Brownson, U.S.N., command- 

 ing), for the purpose of ascertaining the extent of the 

 continental plateau and the border of the oceanic 

 basin, some extraordinary depths have been reached, 

 and successfully measured lay the method of wire- 

 sounding; the specimen-cup and thermometers hav- 

 ing been brought up from depths exceeding five miles. 



The following extracts from the report of Lieut.- 

 Comdr. Brownson, addressed to Prof. J. E. Hilgard, 

 superintendent of the survey, will be of general pub- 

 lic interest. It i's written from St. Thomas, under 

 date of Jan. 29, 1883. 



"I enclose, herewith, approximate positions of 

 soundings taken on lines, first, from Mariguana to 

 Ocean plateau, thence down through Turks Island 

 passage to coast of Hayti, — second line from Samana 

 promontory to Navidad bank, — and thence out to 

 Ocean plateau. . . . From an inspection of the chart 

 to the northward of this island, in connection with 

 the result obtained by me on last line, and the sound- 

 ings taken by Sir George Nares in the ' Challenger,' 

 I thought it more tlian probable that the deep water 

 found by him (3,87.5 fathoms) would extend to the 

 westward. . . . 



" On the 27th inst., in lat. 19° 40' .50", long. 06° 

 23' 40", seventy-one miles west of ' Challenger's ' 

 greatest deptli, with long rolling sea, fresh trade- 

 winds, with frequent squalls of wind and rain, 

 sounded in 4,561 fathoms. In reeling in, cross-heads 

 of sounding-machine sliowed great strain on wire : so 

 shipped cranks to assist reeling-engine over the cen- 

 tre to prevent sudden strain on wire; and, by using 

 every care to ease the strain, we succeeded in re- 

 covering the sounding-rod and thermometer. The 

 bottom was brown ooze ; temperature 36^° F. 



"Fifteen and a lialf miles south-east of the latter 

 station sounded again in 4,223 fathoms, bottom of 

 two layers of ooze, brown on top, with under-strata 

 of gray; temperature 36°. When the wire was nearly 

 in, the reel showed signs of being crushed, cracking 

 in several places ; but fortunately it did not give way. 

 With the last sounding, two bottom-thermometers 

 were sent down, — a Miller Casella No. 49,406, and a 

 Tagliabue No. 531. The latter came up crushed by 

 the excessive pressure. The reading of the Miller 

 Casella I have no reason to doubt. 



" I doubt if the sounding machine and wire has 

 ever before successfully withstood so great a strain. 



" In the soundings taken by Capt. Belknap in the 

 Pacific, in no case that I can find were the sounding- 

 rod and bottom-tliermometer recovered in over 4,356 

 fathoms. 



" In the second sounding, the wind had freshened 

 considerably, and there was a short ugly sea in addi- 

 tion to the long swell." 



survey. 



The Grand Canon Group. — Marble Canon and the 

 Grand CaSon constitute together a continuous gorge, 

 through which the Colorado river courses for 250 

 miles. The walls of the gorge are not sheer preci- 

 pices, but are terraced on a grand scale ; the succes- 

 sion of platforms and cliffs being determined by the 

 succession of strata, which, for the most part, lie hori- 

 zontal. The top of the wall is everywhere upper 

 carboniferous ; and thence downward for about 4,000 

 feet there is a nearly uniform system of paleozoic 

 rocks, conformable in dip. The principal member 

 of this conformable series is so massive that the cliff 

 formed by it is unscalable at nearly all points; so that 

 almost the only access to the deptlis of the gorge has 

 been by boats. In Major Powell's first exploration 

 of the Colorado, he discovered at the head of the 

 Grand Caiion, where the gorge is deepest, a system of 

 inclined rocks wliich had been greatly eroded before 

 tlie deposition of the conformable series. These un- 

 conformable rocks, which he named the Grand Canon 

 Group, rest in turn upon schistose and granitoid rocks 

 having the general facies of the archean. The diffi- 

 culties of the voyage, and especially the exhaustion 

 of supplies, rendered It impossible for him to make 

 extended search for fossils ; and, in lack of paleonto- 

 logic evidence, he assigned the Grand Caiion Group 

 provisionally to the Silurian, and referred the whole 

 of the conforming series above it to the carboniferous. 

 Mr. Gilbert, examining soon after the section at tlie 

 lower end of the gorge, discovered no unconformity, 

 except that between tlie metamorphic and non-meta- 

 morphic rocks; and, finding Cruziana in the lowest 

 member of the unaltered rocks, he referred it pro- 

 visionally to the lower Silurian. He named this 

 member the Tonto Group. Still later Mr. C. D. Wal- 

 cott, making a careful study of the section at an 

 intermediate point, discovered an unconformity by 

 erosion above the Tonto, and at the same time ob- 

 tained additional fossils which served definitely to 

 place the Tonto in the Cambrian. The question then 

 arose, whetlier the unconformity by erosion, observed 

 by Walcott, was the equivalent of the unconformity 

 by dip observed by Powell. If it was, then in Powell's 

 section the Tonto lay immediately aljove the archean, 

 and the Grand Caiion Group was Cambrian. If it 

 was not, then the Tonto was to be found at the base 

 of Powell's conforming series, and the Grand Canon 

 Group was Pre-Cambriau. For the sake of settling 

 this question, and at the same time of exploring the 

 Pre-Carabrian rocks, if such they should prove to be. 

 Major Powell, last autumn, made an excursion to the 

 locality, with great difficulty constructing a liorse- 

 trail from the upper plateau to the brink of the river, 

 where the rocks are best exposed. He found the 

 Tonto at the base of the upper series, and thus de- 

 monstrated the Pre-Cambrian age of tlie Grand Caiion 

 Group. The rocks being unmetamorphosed, and the 

 series having a thickness of more than ten thousand 

 feet, there is great reason to hope that they will prove 

 fossiliferous, and thus .add a prefatory chapter to the 



