May' i, 1884J 



NA TURE 



problems of extension and rupture. The same gentleman 

 has both discovered and applied a new and most remark- 

 able phenomenon in friction ; the fact, namely, that if we 

 give a rotary motion to a body which is in contact with 

 another, not only is the friction diminished in the direction 

 of motion, but the friction in the perpendicular direction 

 is also diminished, apparently in at least an equal degree. 

 Hence, for instance, by rotating the leather packing of an 

 hydraulic ram, it becomes quite free to move in its 

 cylinder in obedience to a difference in pressure on one 

 side or the other. Here we have, once more, science helping 

 art, and art in return throwing light upon the path of science. 

 These facts, and others like them, are encouraging 

 signs, but we must repeat that something more than signs 

 is needed. The work must be not only begun but 

 finished, the bonds of union must be drawn close, and 

 that quickly, or England will rind that it is too late, and 

 that she is once more ready to do the work of the world 

 just when the world has left her no work to do. 



FORSTER'S "STRATA OF THE NORTH OF 



ENGLAND " 

 A Treatise on a Section of the Strata from Newcastle to 

 Cross Fell. ByWestgarth Forster. Third Edition, re- 

 vised and corrected to the present time by the Rev. 

 W. Nail, M.A., with Memoir. Svo. (Newcastle-upon- 

 Tyne, 1S83.) 

 THE position of Forster's " Strata" among the classics 

 of geological literature in England is so well defined 

 that a reissue would be welcome to many readers, as 

 although the progress both of coal and metal mining during 

 the long interval that has elapsed since the appearance of 

 the last edition in 1S21 has done much to supplement, and 

 in some instances modify, the author's evidence, it must 

 ever remain as a splendid monument of geological inves- 

 tigation as carried on in the earlier years of the century. 

 Unfortunately, in the present issue the editor has carried 

 out his duties in a very thorough-going fashion ; to use 

 his own words, " Some alterations have been made in this 

 edition of the 'Strata.' Parts I. and II. have been re- 

 vised and rearranged ; Part III. has been partially recast ; 

 some of the old sections have been extended, and other 

 sections have been given ; obsolete matter has been ex- 

 punged, and new matter in the form of notes has been 

 added." 



If the editing had been confined to the last-mentioned 

 additions, or rather if all the alterations had been supplied 

 as footnotes or in the form of appendixes, such a course 

 would have been perfectly justifiable, and the value of the 

 text would have been enhanced ; but from the course 

 adopted of shifting the original text backwards and for- 

 wards to bring it into harmony with more modern views, 

 and rearranging the sections even to the extent of renum- 

 bering the beds of limestone in the lead-measures, and the 

 intercalation of new subdivisions in the limestone series 

 not contained in the original, the work has become so 

 strangely metamorphosed that any one taking it for what 

 it professes to be, namely, Westgarth Forster's " Strata," 

 will be liable to be strangely misled, unless he carefully 

 compares it with the original text. This is much to be 

 regretted, as the editor's work has evidently been a labour 

 of love, and it is strange that he should have so ill-used 

 his favourite volume. 



The editor has, however, done one good service de- 

 serving grateful mention by supplying a memoir of the 

 author, which is, however, eccentrically interpolated 

 between the original table of contents and the text. From 

 this we gather many interesting particulars of the life of 

 one who may be regarded as the prototype of the Sop- 

 withs, Bewicks, and other mining engineers in the north 

 of England, who have become famous not only in their 

 original districts, but in all parts of Europe and America. 

 It is somewhat surprising to learn how in the year 1807 the 

 material for the first edition of the " Strata " was collected 

 by Forster, who for that purpose resigned the agency of 

 the Allendale lead mines. The volume was issued in 

 1809 in the same year with William Smith's first geologi- 

 cal map of England, and at once became exceedingly 

 popular ; and thenceforward the author was recognised 

 as one of the leading men in his profession, and was fully 

 engaged in many surveys until his retirement in 1833. 

 During this active period of twenty-three years he worked 

 in nearly all the mineral districts of England and Wales, 

 with the exception of Cornwall and Devon, and also 

 visited Spain and North America. The American trip was 

 made in 1831, in pre-steamboat days, in the fine packet- 

 ship Napoleon, making a fairly good voyage of thirty-two 

 days across the Atlantic. The districts visited were 

 Pottsville and Mauch Chunk, in the anthracite district of 

 Pennsylvania, which had then been discovered only eight 

 years, and the Phoenix Copper Mines in Connecticut. 



The later years of his life were clouded by misfortunes 

 due to losses in working some lead mines in Wales, and 

 before the spring of 1829 he had spent nearly all that he 

 possessed in abortive trials, at a period of extreme de- 

 pression in the lead trade. In 1833-34 failing health led 

 him to retire from active work, and on November 9, 1835, 

 he died at Garrigill, in Cumberland, in his sixty-third 

 year. In the author's words, Forster rendered valuable 

 service to the sciences of mining and geology, and for that 

 service, if for no other reason, his name will continue to 

 be remembered for a long time to come. H. B. 



OUR BOOK SHELF 



A Manual of Chemistry. Bv Henry Watts, B.A. (London: 

 Churchill, 18S3.) 



This work is stated by the author to be intended for a 

 student commencing the study of chemistry, and, as he 

 states in his preface, this volume commences with a short 

 sketch of the more important elementary bodies, the 

 principal laws of chemical combination, and the repre- 

 sentation of the constitution and reaction of bodies by 

 symbolic notation. In addition to this there is a large 

 section on chemical physics, including the mechanical 

 properties of gases and the chief phenomena of heat, 

 light, magnetism, &c. For an elementary work, as 

 intended by the author, it is somewhat dense, and would 

 be certainly apt to frighten a beg ner in chemistry. The 

 sections on physics alone, compris g Part I., occupy very 

 nearly 150 pages, and within this narrow space we find 

 that in the domain of light we have refraction, reflection, 

 circular polarisation, &c, treated at considerable length. 

 In magnetism and electricity we have a very complete 

 and exceedingly condensed mass of information, certainly 

 much too complete and condensed for an elementary 

 text-book. In the purely chemical section, forming Part 

 II., the work is extended so as to include a considerable 

 chapter on crystals and the more recent extensions of the 

 atomic theory, and also to the so-called rare metals, 



