July 31, 1913] 



NATURE 



553 



will have no hesitation whatever in endorsing this 

 statement ! 



While a great many notions are introduced into 

 the text in such a way as to make them appear 

 useless, uninteresting, and unintelligible, many of 

 the most important points in a rational system of 

 mathematical education receive little or no atten- 

 tion. Take the broad, general notion of a function, 

 so simple that it can be explained to anyone who 

 is sufficiently unmathematical to understand com- 

 mon sense. It is well illustrated in the case of 

 the senior wrangler who entered the Stock Ex- 

 change and began to apply algebraic methods to 

 the money market. He failed because he had 

 omitted to take account of political considerations. 

 Here was a case where the result was a function 

 of a number of variables, and he treated some of 

 these variables as constant. The senior wrangler 

 was not sufficient of a mathematician. The mere 

 failure to enumerate all the variables in a function 

 occurring in everyday life represents a national 

 loss of millions per annum. Prof. Perry says : — 



" I must confess, however, that the compilers of 

 modern school algebras must make the gods laugh 

 over the uses to which they put this plotting of 

 functions." 



They certainly will do so when they read this 

 book. 



All this is a very great pity. Most modern 

 matnematieal teachers are only too glad to get 

 " formula " questions for their pupils dealing with 

 beams, expansion of steam, flow of water through 

 pipes, electrical resistances, and other practical 

 considerations which familiarise the student in the 

 use of algebraic formula? and equations. We 

 believe they can get the questions they want from 

 this book, and, on the other hand, when it comes 

 to methods of teaching, every teacher naturally 

 prefers his own. But if the substance of the 

 text is a fair indication of what is meant by 

 "practical mathematics," we agree with Prof. 

 Perry's remark (p. xiii.), which, when quoted 

 without its context, reads to the effect that 



"The subject of practical mathematics is, I am 

 happy to say, a subject which is not likely to 

 commend itself to such institutions, nor are such 

 text-books likely to be of much use to real 

 students." 



Evidently neither "academic" nor "practical" 

 mathematics supplies exactly what is wanted. 

 They both have one fault in common, namely, that 

 they place difficulties before the student without 

 any rhyme or reason. Mathematics is not in 

 itself difficult or uninteresting; a child of three 

 can invent a theory and notation for 

 minus quantities without any assistance, help, or 

 encouragement whatever. What we want is a 

 NO. 2283, VOL. 91] 



subject that might be better described as "com- 

 mon-sense mathematics." Teachers are striving 

 after this ideal, and it is very valuable and im- 

 portant to see clearly, as this book shows, that for 

 the attainment of this ideal something more than 

 "practical" mathematics is necessary. 



G. H. Bryan. 



AN EGYPTIAN DESERT. 

 The Geography and Geology of South-eastern 

 Egypt. By Dr. John Ball. (Survey Depart- 

 ment of Egypt, Cairo.) Pp. 394. With Maps 

 and many Illustrations. 



THE area described in this latest monograph 

 issued by the Geological Survey of Egypt 

 is the southern part of the Eastern Desert — a 

 district little known, and inhabited only by nomad 

 Arabs of the Ababda and Bisharin tribes. 



From north to south, this country is intersected 

 by a mountainous axis which rises to heights 

 of from 3000 to more than 5000 feet, and consists 

 mainly of granite, diorite, gabbro, and other 

 plutonic rocks. Eastward from this axis a series 

 of Wadys run down, somewhat steeply, to the 

 shores of the Red Sea on the east, these shores 

 being almost everywhere bordered by coral reefs, 

 which render the coast one of the foulest in the 

 world for shipping. Westward from the moun- 

 tain axis another series of Wadys lend down more 

 gradually to the basin of the Nile. Dr. Ball, who 

 is an accomplished surveyor as well as a geologist, 

 has been able to add much to our knowledge of 

 the physiography and scenery of this almost un- 

 explored country. While devoting his chief atten- 

 tion to the geological features of the district — his 

 discussion of the petrology being especially full 

 and well illustrated — the author has been able to 

 supply much new and interesting information con- 

 cerning the antiquities, the plant and animal life, 

 and the inhabitants — their languages, industries, 

 and customs. 



From, a very early period the district has been 

 credited with the possession of considerable 

 mineral wealth, especially famous having been its 

 gold-mines and emerald workings. Dr. Ball's re- 

 searches, however, do not give much support to 

 the belief that the district may in the future become 

 a great mining centre. 



It is true that very numerous small workings 

 scattered all over the country show how wide and 

 persistent has been the search for gold within 

 the area. There do not appear to have been any 

 alluvial workings, but numerous quartz veins, 

 intersecting all the crystalline rocks of the district, 

 sometimes containing calcite with ores of 

 copper and iron, vield minute quantities of gold, 



