228 



KNOWLEDGE. 



[October 1, 1895. 



lands, of varying extent in different parts, wbich surround 

 the third or treeless zone in the interior. The Rev. R. 

 Baron, for manj- years a missionary in the island, has given 

 an account of its vegetation in the Journal of the LimxTan 

 Society. He estimates the tract of country covered by forest 

 to be about thirty thousand square miles, or one-eighth of 

 the island, but destruction of trees by the natives is taking 

 place with great rapidity. For example, no fewer than 

 twenty-five thousand were cut down to make room for the 

 passage of a tombstone quarried at a distant place. Dr. 

 Wallace, in his " Island Life" and " Darwinism, " insisted 

 on the diversity of the vegetable productions of Madagascar 

 from thcseof the neighbouringAfrican continent, but recent 

 researches on the flora seem to show that it is efsentially 

 African, although it contains a large endemic element. 

 — .-♦-, — 

 Some time ago, one of our correspondents was informed 

 of " an extraordinary squirrel " to be seen in a well-wooded 

 part of an estate on the confines of Westmorland and 

 Lancashire. On interviewing the gamekeeper, who in this 

 instarce happens to be an intelligent naturalist, he found 

 that there was in the woods a squirrel of normal character, 

 except in its tail, which was perfectly white. After several 

 long and silent vigils, well out of sight, our correspondent 

 was rewarded with a sight of the squirrel, a male, in 

 company with a female. The reports had in no way been 

 exaggerated. The animal was of ordinary size and colour 

 except for its tail, which was perfectly white. This is, no 

 doubt, a very unusual occurrence. It was seen by our 

 correspondent, and there was nothing of the " cream 

 colour " peculiar to the coat of the squirrel later in 

 the year. On a neighbouring estate the squirrels have 

 developed extraordinary carnivorous propensities, destroying 

 young birds by dozens. Had they confined their depreda- 

 tions to ordinary wild birds, the " acquired habit " might 

 have become hereditary, and even infectious ; when they 

 attacked the young pheasants, however, their fate was 

 sealed, and an order has gone forth to " clear out the 

 squirrels." Mr. Lydekker,iu Hritish Mamiiuils, of "Allen's 

 Naturalist's Library," p. 171, has referred this occasional 

 habit of squirrels to " only a depraved taste," which, 

 however, does not account for its origin, or for the 

 undoubted fact that it is a taste more prevalent than is 

 generally believed, and therefore " more honoured in the 

 breach than in the observance." 



M. Piltschikoft', in doEcribing recent photographs of 

 lightning, names three t)pe3 of flash — "band-lightning, 

 lube-hghtning, and waterspout lightning." The first two 

 he found to occur in all storms, the third he met with once 

 only. From the measured width of the band-lightning on 

 photographs, and the computed distance, he estimates the 

 actual widths to be from about fifteen to eighty yards. 



Notias of Boofts. 



Fi7>;ier-Prinf Directories. By Francis Gallon, F.R.R. 

 (Macmillan.) Three years ago, Mr. Galton gave, in his 

 " Finger-Prints," an account of the patterns of thumb and 

 finger marks, and discussed their bearings on questions of 

 heredity and racial distinction. In the present volume he 

 shows conclusively that these patterns admit of easy 

 classification, and offer a simple and trustworthy means of 

 identification. To take a pattern, the tip of a thumb or 

 finger is lightly rolled from one side to the other upon a 

 slab having printers' ink upon it, and is then pressed upon 

 paper or cardboard. Impressions are thus obtained of the 

 papillary ridges, well seen at the bulbs of the fingers and 

 thumbs, and the directions, terminations, and junctions of 



the printed ridges can afterwards be examined at leisure by 

 means of a lens, and classified. It is estimated that the 

 chances of two finger-prints being identical is less than 1 

 in 64,000,000,000. Two finger-prints exactly alike may, 

 therefore, be safely concluded to be prints from the same 

 person ; hence the patterns furnish a sure method of 

 proving identity. The diflBculties in the way of the 

 application of this method of identification have gradually 

 been overcome by Mr. Galton, who shows in the volume 

 before us how finger-prints can be indexed so as to be found 

 as easily as a householder can be discovered by reference 

 to a directory. The present writer can personally testify 

 to the efficiency of the methods described. A few weeks 

 ago he went to the Anthropometric Laboratory at South 

 Kensington, and, after giving his finger-prints in the usual 

 manner, asked to be identified, as his impressions had 

 been taken about four years previously, and had been put 

 away with his name upon them. In less than three 

 minutes Mr. Galton's assistant had examined the new 

 impressions, and had picked out from more than two 

 thousand cards the one containing the old prints and the 

 name of the writer. A readier method of identification 

 could hardly be desired. How the result is attained may 

 be learned from the pages of the book under review. The 

 legal profession generally should add the book to their 

 libraries, and the prison officials, under whose direction 

 finger-prints of criminals are now taken, will find it 

 essential to the right understanding of their duties. We 

 would finally remark that the collection and investigation 

 of finger-prints is open to everyone, and with Mr. Galton's 

 new volume, containing fac-simLles of finger-prints and full 

 explanations of what they teach, a student will be enabled in 

 a short time to become an experienced finger-print detective. 



The Mif/ration of British Birds. By Charles Dixon. 

 (Chapman and Hall.) Apart from the deep interest which 

 must be attached to any book dealing with the migration 

 of birds and their dispersal over the globe, Mr. Dixon's 

 present work should commend itself tn every ornithologist 

 on account of the freshness in the manner iu which the 

 subjects are treated. We can but admire Mr. Dixon for 

 his boldness in advancing new theories absolutely con- 

 tradictory to those already advanced and generally accepted 

 by other naturalists, yet we regret the way in which he 

 unnecessarily doubts the correctness of observations made 

 by men whose experience should be at least as good as his 

 own. The book is divided into two parts ; the first and 

 larger portion dealing with the dispersal of birds, and the 

 fecond with their migration. Mr. Dixon dwells at some 

 length on past geographical mutr.tions and glacial epochs, 

 and it is chiefly upon these and a " New Law of Dispersal " 

 that he bases his conclusions. The main feature of the 

 book, and one which is carried all through it, is what the 

 author is pleased to call a " New Law of Dispersal." A 

 new theori/ would have been a more correct term than 

 " law," for we cannot see that Mr. Dixon has brought 

 forward a sufficient number of facts to prove the coi'rect- 

 ness of his "law." Briefly stated, Mr. Dixon's "New 

 Law " is that northern hemisphere Ep:cics of birds never 

 increase their range in a southern direction, and that 

 southern hemisphere species never increase their range 

 in a northern clirection. This law, says the author, is 

 proved by the fact that there is no immigration route (of 

 northern hemisphere birds) which trends south in spring 

 or north in autumn. But before we can recognize the 

 proof of the law, we have to accept as true the author's 

 statement that the present migration of a species is a 

 recapitulation of the past range expansion of that species. 



With regard to the general phenomenon of migration, 

 which 30 many have sought to explain, we do not think 



