HARDWICKE'S SCIENCE-GOSSIP. 



213 



GEOLOGY, &c. 



Rate of Surface Denudation. — The following 

 results are extracted from among numerous others 

 given in a paper by Mr. Mellard Reade, F.G.S., 

 entitled "Denudation of the Two Americas," a 

 presidential address to the Liverpool Geological 

 Society. The proportion of total solids in solution in 

 the Mississippi, a few miles above New Orleans, has 

 been estimated by analysis to be ^ n by weight of the 

 water. This amount is reckoned to give in round 

 numbers about 150,000,000 tons or So square miles 

 of rock 1 foot thick discharged per annum by the 

 Mississippi into the Gulf of Mexico ; and the propor- 

 tion of sedimentary matter has been estimated at 

 over 362,000,000 tons. The rate of removal of the 

 surface of the basin of the Mississippi, taking into 

 account both the dissolved and the suspended matters, 

 is taken to be about a foot in 4,500 years. Attention 

 is drawn to the fact that over 20,000,000 tons of silica 

 are annually poured into the sea by this river, as a 

 remarkable fact, when the usual apparent insolubility 

 of silica is remembered. A sample of water from the 

 Amazon showed of dissolved solids only TBgg5 of its 

 weight, or roughly 160,000,000 tons discharged per 

 annum, or 50 tons per square mile per annum. Mr. 

 Reade thinks that a former estimate of his as to the 

 general rate of solution by rain for the whole world 

 is not far wrong, viz. about loo tons of rocky matter 

 per English square mile per annum, -j^g of a foot per 

 annum being removed in a soluble form every year 

 from the surface of England and Wales. There seems 

 to be in river water about three times as much matter 

 carried down in suspension as in solution. 



Mr. A. J. Jukes-Browne on Stratigraphical 

 Arrangement. — Mr. A. J. Jukes-Browne, in a paper 

 on rock-classification in the "Geological Magazine" 

 for July, gives a Table showing some new proposals 

 for nomenclature. He divides the Tertiary into two 

 systems, the Hantonian (from Hampshire), which 

 contains the Eocene and Oligocene ; and the Icenian 

 (from the Iceni), a name formerly proposed, with a 

 narrower meaning,'by Dr. S. P. Woodward, and which 

 includes the Miocene, Pliocene, and Pleistocene. His 

 systems thus become the Icenian, Hantonian, Cre- 

 taceous, Jurassic, Triassic, , Carboniferous, Devo- 

 nian, Silurian, Ordovician, Cambrian, Archaean or 

 Pie-Cambrian. The primary divisions of the Ordovi- 

 cian are the Arenig Grits, Llandeilo Flags, and Bala 

 Rocks ; those of the Silurian being the Valentian 

 (lowest), Salopian, and Clunian (forest of Clun). The 

 Permian becomes merely a primary division under the 

 name of Dyas. The Wealden and Neocomian are 

 placed together as a group or stage of the Lower 

 primary division of the Cretaceous system, followed 

 immediately above by the Vectian or Lower Green- 

 sand, the name Vectian being derived from the Isle 



of Wight. This paper will repay perusal by those 

 interested in Stratigraphical Geology. 



Since the above was written a paper has appeared 

 in the same journal for last month by Dr. Henry 

 Hicks, F.R.S., in which he proposes to use the term 

 Cambrian as one of the main divisions of the 

 Palaeozoic Rocks, the others being the Devonian and 

 Carboniferous. The Cambrian he would subdivide 

 in descending order into Silurian, Ordovician, and 

 Georgian primary divisions, the latter name being 

 taken "from the districts bordering St. George's 

 Channel, where the lower rocks (Llanberis, Harlech, 

 Menevian, &c.) are best exposed, and where they 

 have been mainly examined." He says it may be 

 found advisable to group the upper system also of the 

 Palaeozoic Rocks into one system, in which case the 

 Devonian would be placed as the lowest of three 

 Primary Divisions. He prefers for subordinate 

 divisions, as far as possible, geographical terms with 

 wide applications. 



Fossil Algve at Kirkcaldy. — In a large exca- 

 vation made at the Kirkaldy Gas Works, a stratum 

 previously unknown as existing here was cut through, 

 and found to contain many fossils, apparently of 

 wood. On making transparent sections of them for 

 microscopic examination, however, I found that they 

 are fossil algae, having a very near agreement with 

 sections of recent stalks of Laminaria digitata and 

 L. saccharina. Like the Laminaria, the sections 

 show three regions, in the centre, a large circular 

 division of irregular cellular tissue ; surrounding it, 

 a broad zone of parenchyma with large cells, which 

 are somewhat longer vertically than their horizontal 

 diameter, as is seen by longitudinal sections ; round 

 this another broad zone of parenchyma, in which the 

 cells are smaller and arranged in radiating rows ; then 

 the epiderm. The three zones occupy about equal 

 breadths. The largest stems I have seen are about 

 four inches in diameter. Mr. Macpherson, manager 

 of the gas works, has two of this size, and about four 

 or five feet long. There is abundance of pieces of 

 smaller size, many of them flattened, and there will be 

 no difficulty in procuring these fossils for months to 

 come, as the excavated stuff is laid on the beach, and 

 the washing of the sea seems to separate the fossils 

 and make them more easily seen. It is worthy of 

 notice that the outside of the fossils has a very great 

 resemblance to that of recent Laminaria which have 

 been washed ashore and dried. The sections of the 

 fossils — both cross and longitudinal — stand grinding 

 well, and are very beautiful. The stratum is situated 

 in the Carboniferous formation, and there are two 

 seams of coal, about eighty feet apart, not very far 

 below it, which have been anciently wrought. I 

 propose to name the fossil in my collection of slides 

 Halophytis magnum till I hear something about it 

 — John Sang. 



