Feb. 12, 1880] 



NATURE 



553 



intervals of rest. And the greatest eruptions have gene- 

 rally indicated the last phase of long periods of moderate 

 activity, periods that escaped the notice of the early 

 ■writers. The true history of Vesuvius could not have 

 heen written until after the establishment of the present 

 observatory. The seismograph of the observatory gives 

 the most accurate indications of the eruptive attempts 

 {dei conati eruttivi) of the mountain and of the degree of 

 its dynamic activity." 



Two other facts require to be alluded to before we close 

 the history of Vesuvius in 1 879. The one is the alleged 

 discovery by Prof. Scacchi of a new element in the yellow 

 and green incrustations found on the lava of 1631. The 

 former of these he believes to be vesbiate of aluminium, 

 the latter vesbiate of copper. The element is named 

 Vcsbium, from an old name of Vesuvius mentioned by 

 Galen. The subject requires further investigation before 

 we can assert with any confidence that a new element has 

 been discovered. 



The second fact is that the Vesuvius railway, from the 

 base to the summit of the cone, more than 1,000 feet, 

 with an average slope of 32 , has been commenced, and 

 is progressing thus far favourably. The work is slow, but 

 labour is che.ip ; we saw fifteen men dragging a single 

 beam of wood up the cone. We are inclined to regard 

 the whole thing as a very hazardous commercial under- 

 taking. For to begin with, if the company charges 20 

 lire for each ascent, it will be long before a fair interest 

 can be paid on the original cost and the working expenses. 

 Moreover, the property is insecure, a stream of lava on 

 the south-west side of the cone would destroy the line 

 at once, and a violent earthquake would throw all the 

 machinery out of gear. G. F. Rod well 



THE CRAYFISH 1 



" /^OMMON and lowly as most may think the crayfish, 

 V_- it is yet so full of wonders that the greatest 

 naturalist may be puzzled to give a clear account of it." 

 These words from von Rosenhof, who in 1755 contributed 

 his share to our knowledge of the animal in question, are 

 cited by Prof. Huxley in the preface to the careful account 

 of the English crayfish and its immediate congeners, 

 which forms the latest volume of the International Scien- 

 tific Series. The book is not designed for " general 

 readers," those somewhat luxurious but presumably intel- 

 ligent persons for whom so much scientific knowledge is 

 chopped and spiced at the present day. It is, as we 

 gather from the author's statement, intended as an intro- 

 duction to serious zoological study, for those who will turn 

 over its pages, crayfish in hand, and carefully verify its 

 statements as to details of structure with scalpel and 

 microscope. To these and also to those who are already 

 well versed in cru = tacean anatomy, the book will have 

 great value and interest ; to the latter more especially, 

 as showing how in the careful study of one organism we 

 are " brought face to face with all the great zoological 

 questions which excite so lively an interest at the present 

 day," and as an exhibition of that "method by which 

 alone we can hope to attain to satisfactory answers of 

 these questions." 



A crayfish is treated in this volume from the point of 

 view of " science," and in the first pages we have some 

 excellent observations (recalling earlier remarks of the 

 author's in the same sense) directed to clearing up that 

 mystery which good people will insist on throwing 

 around that ever-more-widely-heard term. " Common 

 sense," says Prof. Huxley, "is science exactly in so far 

 as it fulfils the ideal of common sense ; that is, sees facts 

 as they are, or, at any rate, without the distortion of 

 prejudice, and reasons from them in accordance with the 

 dictates of sound judgment. And science is simply com- 



' " The Crayfish ; an Intr. duciion to the Study of Zoology." By T. H. 

 Huxley, F.R.S. (London: Regan Paul, 1880.) 



mon sense at its best, that is, rigidly accurate in obser- 

 vation, and merciless to fallacy in logic." In the pre- 

 ceding quotation Prof. Huxley is (in a legitimate and in- 

 telligible way 1 using the word "science" in place of "that 

 quality of mental activity by which science is produced." 

 Immediately afterwards he speaks of science as the pro- 

 duct of certain mental operations, in a passage which 

 possesses great beauty whilst setting forth fundamental 

 but neglected truths as to the source and scope of human 

 knowledge. " In its earliest development knowledge is 

 self-sown. Impressions force themselves upon men's 

 senses whether they will or not, and often against their 

 will. The amount of interest which these impressions 

 awaken is determined by the coarser pains and pleasures 

 which they carry in their train or by mere curiosity ; and 

 reason deals with the materials supplied to it as far as 

 that interest carries it, and no farther. Such common 

 knowledge is rather brought than sought ; and such 

 ratiocination is little more than the working of a blind 

 intellectual instinct. It is only when the mind passes 

 beyond this condition that it begins to evolve science. 



Fig 1. — \stacusjlnviatilis. — The third or external mavillipede of trie left 

 side ■" -■)■ l*. lamina, and br, branchial filaments of the podohranchia ; 

 cxp. coxopodite; cxs, coxonoditic seta;; bfi t basipodite ; ex, exopodite; 

 />. ischiopodite; »tp, meropodite ; cp, carpopodite; //, propodite; dp, 

 daclylopodite. 



When simple curiosity passes into the love of knowledge 

 as such, and the gratification of the aesthetic sense of the 

 beauty of completeness and accuracy seems more desir- 

 able than the easy indolence of ignorance ; when the 

 finding out of the causes of things becomes a source of 

 joy, and he is accounted happy who is successful in the 

 search, common knowledge passes into what our fore- 

 fathers called natural history, from whence there is but 

 a step to that which used to be termed natural philosophy, 

 and no* passes by the name of physical science. 



"In this final state of knowledge the phenomena of 

 nature are regarded as one continuous series of causes 

 and effects ; and the ultimate object of science is to trace 

 out that series, from the term which is nearest to us, to 

 that which is at the farthest limit accessible to our means 

 of investigation. 



" The course of nature as it is, as it has been, and as it 

 will be, is the object of scientific inquiry ; whatever lies 

 beyond, above, or below this, is outride science. But 

 the philosopher need not despair at the limitation of his 



