January 26, 1893] 



NATURE 



299 



tion is turned somewhat intently on the political 

 conditions of the Oriental despotism which has so 

 anomalously maintained itself to the west of our prime 

 meridian. Hence the politician has a temporary interest 

 in what would otherwise have appealed mainly to the 

 geographer and man of science, the publication by the 

 Royal Geographical] Society of a " Supplementary 

 Paper," the " Bibliography of Morocco." This is a 

 work of splendid thoroughness, almost, if not quite, ex- 

 haustive in its list of 2243 titles, and made convenient 

 for reference by two copious indexes of subjects and 

 authors. But it is much more than a catalogue. Com- 

 ments, judiciously brief, but in some cases of exceptional 

 interest extending to a couple of pages, give infor- 

 mation as to little-known authors, or record some 

 striking circumstance in or concerning the books referred 

 to. There is a specially-compiled map, and an introduc- 

 tion which is really an essay on the growth of knowledge 

 regarding Morocco in European countries. With regard 

 to the map, it is explained that only the coast-line has 

 been surveyed. As to the interior : — 



" The best mapped districts are laid down solely from 

 running reconnaisances or sketch-maps. Positions fixed 

 by astronomical observations are i&'N. Many wide areas 

 have never been visited by any Europeans, and most of 

 the Atlas is at this hour as little known as it was in the 

 days of Leo Africanus. There are cities within a few 

 hours' ride of Tangier, which no person capable of 

 giving a correct account of his observations has visited ; 

 and there are others not much farther away, to attempt 

 to enter which — Zarhoun, for example — would, were the 

 intruder detected, be certain death. There is scarcely a 

 river laid down with even approximate accuracy, and, not 

 to enumerate more distant provinces, the entire Riff 

 country, that bold wai'wy which is familiar to the thou- 

 sands who every year sail up and down the Mediter- 

 ranean, is less explored than many regions in the centre 

 of the continent." 



The present population of Morocco is a puzzle almost 

 as difficult, although on a smaller scale, as that of China. 

 The authors of the Bibliography give 4,000,000 as an 

 estimate, but the guesses of various authorities vary 

 between li and 15 millions. The roads shown on the 

 map are mere mule and camel tracks made by the feet 

 of the pack-animals, unaided by any engineer. Ferries 

 are rare, and, of course, bridges are unknown in the 

 interior. The distribution of towns and villages is often 

 at variance with the rules holding for civilised countries. 

 The villages are built out of the way of the main tracks, 

 because people never travel in Morocco for the good of 

 the inhabitants, and it is safer to live off the path of the 

 tax-collector and the Government official, who demands 

 free food and quarters. The great number of place- 

 names on the map of so thinly-peopled a country is 

 due to the fact that the tombs of saints are such important 

 landmarks that they must be indicated, even if only a 

 few persons live beside them. " All the places beginning 

 widh ' Sidi' (Lord, master) are either actually tombs or 

 the tomb has formed, as in so many of our cathedral 

 cities, the nucleus of the town or village." " Sok," 

 another affix of frequent occurrence, means market-place, 

 and many of the established sites for periodical fairs are 

 uninhabited between the gatherings of people from far 

 and near. Many of the place-names on the coast exist 

 in two forms at least — the native word and its Portu- 

 guese or Spanish translation ; Casablanca and Dar-el- 

 beida (both meaning White house) for example. We 

 regret that the authors did not see their way to lay down 

 precise rules for the spelling of Moorish place-names, 

 either by giving a standard transliteration of the Arabic, 

 or a uniform phonetic system. Indeed, even in the 

 introduction a few anomalous spellings are found, e.g. 

 Zarhoun and Zerhun, Moulai and Mowlai. 



The physical geography of Morocco appears to be 



NO. I 2 13, VOL. 47] 



changing, and the natural conditions of the country are 

 less favourable for agriculture than they were a few 

 centuries ago. The forests have been destroyed with 

 such recklessness that the soil has been dried up and 

 swept away in many places ; there is evidence that the 

 rainfall has diminished, lakes have dried, and rivers 

 formerly navigable have become silted up, or alternate 

 as dry tracts of stone and raging torrents. 



In one respect alone— the enthusiastic Moslemism of 

 its people — does Morocco show no sign of degeneration. 

 Although the Moors can no longer seize and hold the 

 Christian slaves, whose stories bulk so largely in the 

 bibliography, their hatred and contempt towards " un- 

 believers " is in no sense abated. Into such a land na 

 Europeans could penetrate far, except in the past as slaves, 

 or now as official messengers of European Powers under 

 special protection, jealously watcttfed and prevented from 

 studying places or people. The last serious attempt at 

 scientific exploration — that of Mr. Joseph Thomson —was 

 again and again almost stopped by the fanatical Kaids, 

 and only his remarkable persistence and daring stratagems 

 carried him as far as he reached. Such stratagems would 

 hardly serve again, and for the present the exploration of 

 the Atlas Mountains, with their half-guessed topography, 

 imperfectly- known flora, and unsurveyed mineral wealth 

 is at an end. The futility of disguise as an aid to ex- 

 ploration is fully proved in the records before us, where 

 the ghastly fate of many who tried to pass as Moslems, 

 and the unsatisfactory results obtained by others who 

 escaped alive, are briefly told. 



It seems to us that an attempt might well be made to 

 open communications with fanatical Mohammedan coun- 

 tries either by explorers or diplomatic agents of the same 

 faith, and there must be many amongst the educated 

 Mohammedans of India who are well suited for such 

 work. The rehgious beliefs of a people with whom belief 

 and conduct are so closely related, must be taken into 

 account in dealing with them, just as much as the phy- 

 sical features of a country. And as Arctic sailors have 

 been proved to be the natural explorers in the Antarctic 

 seas, Swiss mountaineers the safest pioneers on New 

 Zealand glaciers, and Canadian boatmen the most expert 

 in shooting the Nile cataracts, so Mohammedan envoys 

 might be expected to make the most favourable impres- 

 sion on the people of Morocco or of the Mohammedan 

 Sudan. 



Sir Lambert Playfair and Dr. Brown deserve the heart- 

 iest thanks for completing their Bibliography of the 

 Barbary States in such an admirable way, and we do not 

 doubt that the work will be very widely consulted in the 

 immediate futuie. 



THE RATE OF EXPLOSION IN GASES. 



THE following is an abstract of the Bakerian Lecture 

 on " The Rate of Explosion in Gases," delivered 

 before the Royal Society by Prof. Harold B. Dixon, on 

 January 19 : — 



1. Berthelot's measurements of the rates of explosion 

 of a number of gaseous mixtures have been confirmed. 

 The rate of the explosion wave for each mixture is con- 

 stant. It is independent of the diameter of the tube 

 above a certain limit. 



2. The rate is not absolutely independent of the initial 

 temperature and pressure of the gases. With rise of 

 temperature the rate falls ; with rise of pressure the rate 

 increases ; but above a certain crucial pressure varia- 

 tions in pressure appear to have no effect. 



3. In the explosion of carbonic oxide and oxygen in a 

 long tube, the presence of steam has a marked effect on 

 the rate. From measurements of the rate of explosion 

 with different quantities of steam, the conclusion is drawn 

 that at the high temperature of the explosion wave, as 



