May i, 1884J 



NA TURE 



17 



conception was developed in a series of memoirs dealing 

 with chemical types, and was later on generalised and 

 simplified by Charles Gerhardt. 



" Dumas' studies embraced every branch of the science — 

 discovery and description of mineral and organic com- 

 pounds, analysis of numerous substances and improve- 

 ment of the methods of analysis themselves, determina- 

 tion of atomic weights. With the penetration of inven- 

 tive genius he introduced into all his researches that firm 

 grasp of the subject, that accuracy in details, that critical 

 spirit which are the essential conditions and necessary 

 1 instruments of all scientific investigation. 

 I "And howshall I speak of his theoretical views expressed 

 I on a great variety of special subjects, and embodied either 

 in his great ' Traite de Chimie Appliqude aux Arts,' or 

 in his admirable ' Lecons de Philosophic Chimique ' ? 

 J Merely to mention one point, to Dumas we are indebted 

 for a first attempt at a classification of simple 11011- 

 jmetallic bodies, an attempt which has still its value. 

 : " Let me also remind you that, after enriching physio- 

 logical chemistry at the outset of his career, he soon after 

 .endowed physics with a new method for determining the 

 'densities of vapour, in continuation of the work begun by 

 his master, Gay-Lussac. 



" But a complete idea of his influence and authority 

 cannot be had without reference to his career as a teacher. 

 lOn his arrival in Paris he opens a course of lectures at 

 Ithe Athenasum. Later on he founds, jointly with Lavallee, 

 'Ollivier, and Pellet, the Central School of Arts and Manu- 

 factures, where he conducts the chemical class for a 

 jquarter of a century. In 1832 he replaces Thenard at 

 pie Polytechnic, and the same year is appointed Assistant 

 [Professor to the Faculty of -Sciences. In 1S41 he be- 

 comes at once Titulary and Dean of the same Faculty, 

 having three years previously obtained the Chair of 

 Organic Chemistry in the Faculty of Medicine. It was 

 Ihere perhaps that his talents as a teacher achieved their 

 greatest triumphs. He was at that time at the most 

 (brilliant period of his creative genius, and he set forth the 

 great ideas then animating him with sympathetic warmth 

 and persuasion, with -inimitable clearness and wealth of 

 [illustration. 



" Such, in a few words, has been the preponderating part 

 played by M. Dumas in science and instruction. And 

 although during his last years he withdrew from public 

 life, it was only to devote himself to work of another 

 order. He was equal to every undertaking imposed on 

 him, the soul of the many committees over which he pre- 

 sided, the ornament of the Academic celebrations which 

 he honoured by his presence and addresses. And after 

 Buch a long and glorious life what remained except a 

 peaceful end in the midst of his family circle, and in the 

 :ull enjoyment of all his faculties? But such a command- 

 ing figure cannot pass into forgetfulness. Your memory, 

 Dumas, shall be perpetuated, your name transmitted from 

 age to age. You shall live in your works, in the example 

 »'ou have given, in the immortal productions and rare 

 qualities of your mind : Forma mentis ceterna." 



THE EARTHQUAKE 

 "pARTHQUAKES are so rarely observed in England, 

 ,1 — ' that an exceptional interest attaches to that of 

 <\pnl 22, an interest far in excess of that due to its in- 

 Tinsic importance. Fortunately the earthquake is ex- 

 ceptional in another sense. It is seldom that a shock 

 results in so small a loss of human life in proportion to 

 (he damage done to houses. 



The daily London press, for a few days after the occur- 

 ence, gave much information as to the range of the 

 Safthquake, and the nature and amount of the damage 

 {tone ; further details are given in the local papers of the 

 eastern Counties, but we are still sadly in want of definite 

 statements upon many matters of great importance. In 



this article we shall notice only a few points of interest, 

 reserving for a later issue, it is hoped by the aid of fuller 

 knowledge, a more complete account of the phenomena, 

 to be illustrated by a map showing the area of disturbance. 

 The shock was most severely felt near the north shore 

 of the estuary of the Blackwater, and for about six miles 

 inland to the north, in the direction of Colchester. The 

 geology of this district is simple. Nearly all the country 

 is occupied by London Clay ; over the marshy land of the 

 Colne, and the flats separating Mersea Island from the 

 mainland, there is a covering of recent alluvial deposits ; 

 over parts of the higher land of Mersea Island there are 

 patches, from a quarter of a square mile to one square 

 mile in area, of Glacial gravel, the remnants of a great 

 sheet of similar material which once overspread the Lon- 

 don Clay and joined the large area of similar gravel near 

 Colchester. This town is mostly built on gravel, which 

 rises to a greater height, and occurs in considerable thick- 

 ness, to the south-west of the town — over Lexden and 

 Stanway Heaths ; further to the west and south-west this 

 gravel passes under Boulder Clay. Underlying the whole 

 of the Tertiary beds of the east of England there is a con- 

 tinuous bed of Chalk, from 600 to 1000 or more feet in 

 thickness. Below the Chalk there is a bed of Gault Clay 

 of varying thickness. But here our certain knowledge oi 

 the geological structure of the country ends. Rocks of 

 Silurian, Devonian, or Carboniferous age have been 

 proved at various points under the east of England — at 

 Harwich, Ware, Turnford, Tottenham Court Road ; rocks 

 of probably Triassic age have been found at Crossness 

 and Richmond. Still further west and north-west the 

 older rocks have been proved at Burford and Northamp- 

 ton. Over Central England the Jurassic and Triassic 

 rocks cover a wide area, but from beneath these the older 

 rocks appear in numerous places. 



One of the most interesting questions connected with 

 the recent earthquake is to ascertain whether there be 

 any relation between the known range of these older rocks 

 and the range of the earthquake over areas far distant 

 from its central spot. At first it seemed certain that such 

 was the case. The shock was plainly felt at Bristol, 

 Wolverhampton, Birmingham, and Leicester — all places 

 on or near to the outcrop of the older rocks. Numerous 

 intermediate localities have since been mentioned, many 

 not being connected, so far as we jet know, with the near 

 existence of older rocks ; but the far distant places still 

 make it probable that some such connection exists. 



It seems therefore likely that the wider and more 

 general range of the earthquake is connected with the 

 range of the Palaeozoic rocks, whereas the local pheno- 

 mena depend very largely upon the nature and thickness 

 of the Secondary and Tertiary rocks. It is therefore im- 

 portant that those who study in detail the effects of the 

 earthquake on the spot should do so with the aid of the 

 Geological Survey Map of the district, which was surveyed 

 by Mr. W. H. Dalton. The map and explanatory memoir 

 are both published ; in them the nature of the drift 

 deposits are fully explained. 



Almost all earthquakes have a very striking effect on 

 springs and wells, sometimes causing a permanent change, 

 at other times having merely a temporary influence. It 

 is somewhat remarkable that so little has been recorded 

 upon this point. A strong spring at West Mersea, which 

 issues at the base of the Glacial gravel, where this bed 

 rests upon London Clay, is said to have ceased to flow for 

 a short time, and to have been discoloured when the water 

 returned. Any residents in the district who have the 

 opportunity of inquiring into similar cases, which doubt- 

 less occurred, will do good service by noting the facts. 



Dr. J. E. Taylor's letter, which appears elsewhere, con- 

 tains much valuable information, such as might well be 

 collected from neighbouring areas ; his observations as to 

 the twisting of chimneys, &c, and as to the direction in 

 which that twist occurred, is a case in point. 



