Nov. 28, 1889] 



NATURE 



7':> 



blank day in the coldest weather, if I know there are fish 

 in the river." A cold mist coming on will always prevent 

 fish from rising. On a fine .April day, when the sun is 

 bringing down snow water, the time to take fish is after 

 the sun has warmed the river, but before the snow melted 

 by the sun about the sources of the river has had time to 

 run down and chill the water. In both cases it is a 

 question of the relative temperature of the air to the 

 water. 



" Do salmon feed in fresh water } ' is one of the 

 questions the author asks. He answers it in the affirma- 

 tive, as he cannot believe that fish rush at spinning baits, 

 eat prawns, and chew up a bunch of lob-worms simply to 

 gratify the angler's love of sport. It is difficult, indeed, 

 to understand how the theory of salmon living for months 

 in fresh water " on his own fat, which has been accumu- 

 lated while feeding in salt water" — as Dr. Francis Day 

 puts it — could have been accepted by him, or by the late 

 Frank Buckland. Why are good salmon rivers bad 

 brown trout rivers ? Simply because the salmon feed on 

 the trout. 



The question of close time Major Traherne says " is the 

 key to the situation ; in other words, to the adjustment of 

 the various claims of netting proprietors and anglers, as 

 the prosperity of our salmon fisheries, and the increase or 

 decrease of a most valuable article of food depends in 

 great measure upon the periods fixed to suit each river." 

 This means that the proper adjustment of close time to 

 «ach river will divide the clean fish fairly between the 

 upper and lower proprietors, and will also provide 

 abundant spawning fish to fill the beds upon the upper 

 waters. At present the weekly close time in England 

 and Scotland, extending from 6 p.m. on Saturday to 

 6 a.m. on Monday, is too short to enable fish to run past 

 all the nets on many of our rivers ; the upper nets 

 sweeping in on Monday morning most of the fish that left 

 the salt water on Saturday night. Again, the rod fishing 

 is kept open too late. We have constantly seen gravid 

 fish taken in October, out of which the eggs or milt ran 

 when the fish were landed — fish that were neither able to 

 fight, nor fit for food. Late in the season the gravid fish 

 will take any bait as voraciously as the kelts in early 

 spring, and the angler is able to state that he killed his 

 six or eight heavy fish a day. After being kippered they 

 are just eatable, and that is the best that can be said for 

 them. On the other hand, with each of the female fish — 

 and most of the fish killed at the end of the season are 

 hen fish — perish some 20,000 eggs fully developed. All 

 that Major Traherne says about the weekly close time, as 

 well as about the closing of the fishing in the autumn, 

 deserves careful consideration. 



AN ELEMENTAR V TEXT-BOOK OF GEOLOGY. 



An Elementary Text-book of Geology. By W. Jerome 



Harrison, F.G.S. (London : Blackie and Son, 1889.) 



IT is well known that there are certain things, which, 

 like reading and writing, come by nature, such as 

 the driving of a gig, and the management of a small 

 farm. Taese every man can do. And till lately it 

 seems to have been very generally held, that, when a man 

 or woma 1 had shown by repeated failure that he or she 



was hopelessly incompetent to earn bread in any other 

 way, there was nothing to forbid him or her from opening 

 a school for small children : the laying of the foundations 

 of an education was such a simple matter that it was 

 within the reach of everyone. It looks also as if the 

 writing of an elementary text-book on a scientific sub- 

 ject is very generally held to be an equally easy task, 

 at least the bounteous profusion with which such books 

 are showered upon us would appear to point to such a 

 conclusion. But anyone who has tried to teach or to 

 write a book that shall be used for teaching purposes, 

 knows only too well that it is with the beginner and in the 

 elements of his subject that the real difficulty lies. And 

 besides the inevitable obstacles to success which from the 

 nature of things he must meet with here, there are to be 

 taken into account others of a more artificial kind. An 

 elementary text -book must be cheap ; neither author 

 nor publisher can be expected to be wholly indifferent 

 to profits, and only cheap books pay in science ; but, 

 setting this consideration aside, it is of the first importance 

 that the work should be within the reach of the largest 

 number possible of buyers. Cheap, and therefore small 

 and sparingly illustrated. So here arises the first difficulty. 

 What to leave out in the text and how far illustrations 

 may be dispensed with. 



Before these questions can be answered, the author 

 must make up his mind what end he proposes the book 

 shall be made to compass. For there are two most 

 distinct purposes which a text-book may be intended to 

 serve. It may be designed to educate the reader ; or it 

 may be put together in order to help him to get through 

 an examination. And for books of the first kind there are 

 two classes of readers to be provided for : some will never 

 go beyond the elements of the subject ; for others the 

 text-book is only the first step on a journey which will 

 lead them on through all the details and ramifications of 

 its subject. But the needs of both classes are at the 

 outset very much the same. Both want a basis, broad 

 and flat in its simplicity, on which they can plant their 

 feet firmly ; not a surface so rough and jagged with 

 complicated details that they are bewildered to know 

 where, or whether anywhere, a secure foothold is to be 

 found on it. For both the aim of the book must be to give 

 fibre and sinew to the mind, not to pack into it a mis- 

 cellaneous assortment of useful and interesting facts ; the 

 mastery of the book must involve not the mere exercise of 

 memory, but the continuous use of observation and the 

 logical faculty. 



In every branch of science there are certain parts which 

 are eminently fitted to serve these ends, and other parts 

 which will most effectually defeat them if introduced into 

 an elementary work. Now, in the Presidential address to 

 the British Association at the recent meeting at Newcastle 

 the objects which ought to be exhibited in a Museum 

 intended for popular instruction were most lucidly marked 

 off from those that ought not: an almost identical clas- 

 sification will divide those parts of a scientific subject 

 which ought to find a place in an elementary text-book 

 from those that ought not. In the same address an 

 emphatic warning was given against overcrowding the 

 cases. Equally must the writer of a text book be on his 

 guard against congested sentences or chapters. 



Here, as in all education, the course of instruction, if it 



