Jan. I, 1 8 74 J 



NATURE 



159 



at once from the right-hand side of the board, so as to 

 traverse the upper and lower parts of the convex lens, 

 they are made to run into one another, thus illustrating 

 the meeting of rays in a focus. 



Lastly, by using two runners with wheels of different 

 diameters, as the refraction depends on the resistance to 

 the wheels by the velvet, the apparatus may be so inclined 

 as to show plainly their consequent difference of refrac- 

 tive angles. The courses of the two are seen in Fig. 5. 

 This experiment, however, requires some nicety of ar- 

 rangement 



Now the separation of rays of different refrangibilities 

 by a prism being due to a like cause, this experiment 

 serves to illustrate mechanically the decomposition of 

 white light. Let the large-wheeled runner represent 

 the red ray, and the small-wheeled runner the violet ray, 

 the principle of the prismatic spectrum becomes at once 

 evident. 



For the information of any who may wish to reproduce 

 this simple apparatus, I may state the dimensions I have 

 found convenient. The wheels may be if in. and 2 in., with 

 rounded edges, mounted on a nearly half-inch iron axle, 

 turned down to J in. at the ends. The boards may be 2 ft 

 6 in. by i ft. 6 in., with velvet on each side. It is conve. 

 nient to place the velvet nearer to one end of the board 

 to leave room at the other for starting the runner ; and 

 care must be taken to cut the velvet so as to present a 

 good resisting surface, as this varies with the direction of 

 the pile. In using the apparatus for teaching, care in 

 manipulation is required to neutr.ilise the defects of the 

 texture. Some kinds of " LUrccht velvet," to be had from 

 the upholsterers, are more uniform than the " imitation 

 seal-skin," and thus work more equally, but their effect is 

 not so striking. Wet sand will answer equally well with 

 the velvet, if metal wheels be used. 



Edward B. Tylor 



THE FRESHWATER FISH OF INDIA AND 



BURMAH 

 Report on the Freshwater Fish and Fisheries of India 

 and Burniah. By Surgeon-Major Francis Day, F.L.S. 

 and F.Z.S., Inspector-General of Fisheries in India. 

 8vo. (Calcutta, 1S73.) 



IN the introductory part the author states that the pre- 

 sent report is the result of investigations commenced 

 by him in the year 1S68, into whether a wasteful destruc- 

 tion of the freshwater fisheries is or is not occurring in 

 India and Burmah. He comes to the conclusion that a 

 wasteful destruction of fish is going on to a very great 

 extent, that these fisheries arc more and more deterio- 

 rating, and that immediate legislation is called for, to 

 prevent the entire failure of a most important article of 

 food. 



The steps taken by the Inspector-General to ascertain 

 the facts on which he bases his report were twofold. 

 He personally inspected districts of various parts of the 

 Indian Empire, and supplemented his own observations 

 by collecting the opinions of European and Native offi- 

 cials, to whom he addressed a series of questions bearing 

 upon the subject. Accordingly the book before us is 

 divided into two parts : — (i) The report proper, pp. i-i 18 ; 

 and (2) A resiimi of the answers returned, with marginal 



notes by the reporter, pp. i.-ccxxxvi. An article on " Fish 

 as Food, or the reputed Origin of Disease," an Enumera- 

 tion of the Indian freshwater fishes, and Notes on pre- 

 serving specimens of fish, conclude the volume. 



Europeans who have formed favourable ideas respect- 

 ing Indian rivers and their abundance of fishes from the 

 accounts which so frequently enliven the sporting papers 

 of the day, will find them rudely dispelled by this report. 

 It is true that not a few of the resident ofhcials deny the 

 decrease of fishes, and deprecate legislative interference 

 altogether. Thus, for instance, the Commissioner of the 

 Agra Division writes that there is no reason to apprehend 

 that any wholesale destruction of fish goes on in these 

 parts. A close-time might no doubt be introduced by 

 law for the protection of fish during the breeding season, 

 but it does r.ot appear to him that it would be easy to 

 carry out such a measure, or that there is any compen- 

 sating object to be gained ; that " it is a useful maxim — 

 de tiiinimis Hon curat lex — minute legislation is unbefit- 

 ting our position in this country, and more likely to ex- 

 pose our Government to ridicule than to any results of 

 important benefits to the people;" "it is in the highest 

 degree undesirable that the public mind should be dis- 

 turbed by gratuitous interference on the part of an alien 

 administration, enforced by not very trustworthy agency." 

 On the other hand, the Inspector adduces such incontro- 

 vertible evidence in favour of the conclusion he has arrived 

 at, that we can but agree with him that in numerous dis- 

 tricts the freshwater fisheries are in danger of being 

 utterly destroyed, and this must appear to call for speedy 

 interference by the Government all the more, as those 

 districts are among the most populous, in which this 

 article of food can be least spared. 



Naturally one looks first for the causes by which the 

 Indian fisheries are said to have been thus reduced ; and 

 it is not very flattering to be told by the author that this 

 disastrous effect has been caused by the change from the 

 Native to the British rule. He states that, under the for- 

 mer rule, fisheries formed royalties mostly let out to con- 

 tractors, who alone in the district possessed the right to 

 sell fish, and that they permitted the people, on payment, 

 to capture fish for their own consumption ; that the men 

 who followed the occupation of fishing form.ed distinct 

 crafts or castes, exercising their calling with certain re- 

 strictions and regulations. Under British rule the renting 

 system was abolished ; with the most philanthropic 

 intentions, the British gave to the people liberty to fish 

 when and where they pleased ; where everybody could fish, 

 fishing ceased to be a distinct calling ; breedingfish were 

 captured without regard to season ; and when the supply 

 of larger fish commenced to fail, it became the practice 

 to catch undersized fish and fry. Add to this, that a 

 number of irrigation weirs and dams were erected, pre- 

 venting the fish from resorting to suitable spawning-beds, 

 that fixed engines for the capture of fish are now used, 

 where previously they were never permitted, and the 

 natural result is the lamentable state as represented by 

 the Inspector. 



We need not enter at present into the remedial mea- 

 sures provisionally proposed by Mr. Day. His proposals, 

 as well as the opinions of his opponents, will no doubt 

 find due consideration on the part of the Indian Govern- 

 ment. But I will not conclude this notice, without 



