378 



SCIENCE- G OSSIP. 



GEOLOGY 



CONDUCTED BY EDWARD A. MARTIN, F.G.S. 



pHOSi'HATlc Dei'OSITS. — At the annual meeting 

 of the Geologists" Association on February 2nd, after 

 the report and accounts had been disposed of, the 

 President, iVIr. J- J- H. Teal, M.A., F.R.S., de- 

 livered his address, taking as his subject "The 

 Natural History of Phosphatic Deposits." In view 

 of the phosphatic floors which have been found from 

 time to time in the chalk, the address, when printed, 

 will prove of great interest to students of that formation. 



Museum at Croydon. ^By the energy of the 

 local Natural History Society, the nucleus of a 

 museum has been formed and arranged in the Tow n 

 Hall. Mr. N. F. Robarts, F.G.S. , is acting as 

 curator. For the present the exhibits are almost 

 entirely geological. A fine specimen of Inoaramtis 

 ciivieri is shown from the chalk, also a large flint 

 with seven specimens of Echiiioioints conicus im- 

 bedded therein. 



The Eruption of Krakatoa. — The tremendous 

 eruption of the volcano of Krakatoa in 18S3 will be 

 fresh in the minds of many people, owing to the 

 extraordinary and grandly luminous sunsets which 

 were caused in our islands by the immense quantity 

 of material which was shot up into the air. The 

 finer particles were found to have made more than 

 one complete circuit of the globe. We are indebted 

 for very detailed accounts of the eruption to the work 

 of the Krakatoa Committee of the Royal .Society, 

 which made its report in 1S88, The group of 

 islands of which Krakatoa was the chief lie between 

 Java and Sumatra, and have long been recognised as 

 of volcanic origin, being probably the remains of an 

 immense cone that had at a very remote epoch been 

 shattered by a similar yet grander catastrophe. An 

 eruption had been recorded in 1680 ; but between 

 that date and 1880, when earthquake movements set 

 in, there had been apparently a period of rest. The 

 eruption itself commenced in May 1883, and con- 

 tinued almost without interruption until August 

 26th. The island was then lost under a cloud of 

 black vapour, which it was estimated rose to a height 

 of seventeen miles. Loud explosions were heard, and 

 these gradually increased in intensity and violence, 

 until early on the following day one of fearful 

 intensity rent earth and air. This was followed by three 

 others in the space of about three and a half hours. In 

 two days more the eruption was almost at an end. 

 During the period of greatest eruption a huge dust- 

 cloud travelled in about two hours to Batavia, a hun- 

 dred miles away, and for some hours the town was in 

 complete darkness. There 'was scarcely a place on 

 the globe which did not see the effects of the dust- 

 clouds. The materials are estimated to have been 

 shot up to a height of no less than twenty- five miles 

 above the mouth of the crater, into an area of the 

 atmosphere the rarefaction of which makes this great 

 height the more remarkable. The after-glows seen in 

 our islands in November and December 1883, that 

 created such interest by reason of their beautiful tints, 

 were cau.sed by the iitiinute powdery ilusi which was 



still floating in the atmosphere. The question of 

 greatest interest to geologists is that relating to the 

 after-results of the eruption on the i.sland itself. In- 

 dependently of its effects on the smaller islands Kra- 

 katoa, an island of more than five miles in length, 

 lost in these terrible explosions about two-thirds of 

 itself. Where formerly was land, a depth of 960 feel 

 of sea has been fathomed. .Some of the ejected 

 material had gone to form an extended coast-line 

 elsewhere, whilst great banks of ejected pumice 

 covered the sea for miles. Where all the lost material, 

 the relics of the land, had gone, even now has ni5t 

 been satisfactorily determined. — E. A. Martin. 



The Prehistoric Rhine. — At the Victoria 

 Institute in London, on April 2, a paper by Mr. 

 W. P. T^rvis, F.G.S., was read by Prof. Logan 

 Lobley on " Thalassographical and Thalassological 

 Notes on the North Sea." We print the title in full, 

 but there seems no real necessity for the introduction 

 of these barbarous terms into our language. A large 

 amount of useful detail is given, which has been 

 obtained from various soundings in and about the 

 Norwegian Fjords and on the Baltic coast ; but the 

 theoretical portion of the paper, which deals with the 

 " Palaeo-Rhine," appears to be altogether lacking in 

 proof. After incorrectly quoting from Mr. Harmer's 

 paper, in which Mr. Harmer deals with the former 

 probable ccjurse of the Rhine through the unsubmerged 

 North Sea area, he suggests that it is possible that its 

 course extended northward by what is known as the 

 "Silver Pit." The theory is interesting, and we quote 

 his remarks : — " Fifteen miles out to sea, offthe coast 

 near Grimsby, lies the Silver Pit, well known to 

 fishermen. This remarkable physical feature is a 

 distinctly marked, tortuous, submerged river valley, 

 23 miles long by 2 miles broad, running towards the 

 north. For the first 15 miles the depth of the mid- 

 channel rapidly increases from 40 to 45 and 50 

 fathoms consecutively, bounded by lateral declivities 

 40 fathoms in height ; in other words, by respect- 

 able elevations of 240 feet. Farther on the 

 depth gradually diminishes to 35 fathoms, and finally 

 is only 23 fathoms, beyond which we cannot now 

 follow the valley, which has been quite filled in 

 with sediment. Cromer (Mundesle)') is 33 miles dis- 

 tant to the south-east from the head of the Silver Pit, 

 which we consider to have undoubtedly formed part 

 of the course of the Palaeo-Rhine. There is nothing 

 to surprise us if all evidence of the line the river 

 followed should have been obliterated (as between 

 Holland and Walton), except in this one isolated 

 place, seeing that it ran principally through Tertiary 

 strata with low banks. Possibly the Silver Pit, on 

 the other hand, marks its passage through chalk 

 rocks. What with the strong littoral currents and 

 the detritus caused by the very considerable encroach- 

 ment of the sea on the east coast of Lincolnshire and 

 Norfolk, the wonder is that any trace of the original 

 valley should have come down to our times. If this 

 theory is accepted, we have been enabled to trace the 

 course of the Palaeo-Rhine for 60 miles farther than 

 Mr. Harmer." Mr. Jervis is ingenious in his sugges- 

 tion, but we are unable to see in it more than a 

 suggestion, as proof must of course be lacking. The 

 same may be said of his theory of the extension of 

 the same river to (i) what is now a hundred-fathom 

 sounding in lat. 58° 45' N., long. 0° 22' W. ; and 

 (2) to the channel which now exists between the 

 Orkney and Shetland Islands. An interesting dis- 

 cussion followed the paper, which was remarkable 

 for the statements which were given utterance to l>y 

 Professor Hull. 



