602 



NATURE 



[Apn/ 2<^, 1886 



tion Fund towards the close of the year 1883 organised 

 an expedition for the purpose of making a geological 

 survey, or rather reconnaissance, of Western Palestine, 

 and intrusted its conduct to Prof. E. Hull of the Geo- 

 logical Survey. The Report of this expedition is now- 

 issued as a handsome quarto volume of 145 pp., with 

 maps and numerous woodcuts. Part I. gives an enume- 

 ration of the more important or accessible writings of 

 previous observers, and a description of the physical 

 features of the districts visited. Part II. deals with the 

 geological structure of Arabia Petrasa and Palestine, 

 including the Archaean crystalline rocks, and the Car- 

 boniferous, Cretaceous, Tertiary, and Po5t-Tertiary for- 

 mations. Part III. contains a brief account of the 

 Tertiary Volcanic Rocks. Part IV. is devoted to a dis- 

 cussion of the dynamical operations which may have 

 brought about the present geological structure of the 

 region, and of the evidence of former differences of 

 climate. Part V. treats of the origin of the saltness of 

 the Dead Sea and of the recent climatal changes of that 

 district. The scheme of treatment is thus comprehensive 

 enough, and the details and conclusions are clearly ex- 

 pressed, though they hardly add as much as could have 

 been hoped to what was already known on the subject. 

 The discussion of the dynamical questions is disappoint- 

 ingly meagre. In the problem of the origin of the great 

 Jordan A'alley depression there was room for much 

 detailed exposition, wherein a careful collection of the 

 facts of geological structure could have been made con- 

 ducive to a valuable addition to our knowledge of this 

 important and still obscure branch of geological physics. 

 The history of the surface-features of the region of 

 Western Palestine is a question on which the Report 

 throws very little fresh light, though it is the one to which 

 perhaps above all others the members of a flying corps 

 of observation might have been expected to be able to 

 contribute valuable data. Regarding the changes of 

 climate and the origin of the Dead Sea we should have 

 looked for more new materials and a much fuller dis- 

 cussion than the few paragraphs in which this important 

 subject is dismissed. No doubt Prof Hull and his 

 companions did as much in the way of observation 

 during their brief visit as was possible in the time, and 

 he has made all that probably could be made of it in this 

 Report. But we are inclined to think that the subject 

 was in such a position that little further could be usefully 

 done to it by the rapid journey even of a trained observer 

 through the country. If the Committee of the Palestine 

 Exploration Fund want to have a satisfactory solution of 

 the many profoundly interesting geological problems 

 presented by Syria and Palestine, they must organise the 

 task as part of the less rapid and more detailed survey of 

 the general topography. The Report is excellently 

 printed and illustrated, the maps being of especial value, 

 containing as they do a summary of all that is known up 

 to the present time regarding the distribution of the rocks 

 in Palestine. There are some errors of the press which 

 on revision the author will no doubt correct in another 

 edition, and we would call his attention to a sentence 

 which betrays his nationality, " The Patriarch Job, 

 whether an actual person or a representative character, 

 may be supposed to have inhabited the Plains of Edom " 

 (p. 123). 



A MANUAL OF CHEMISTRY 

 A Short Manual of Chemistry. Vol. I. " Inorganic 

 Chemistry." By A. Dupr(^, Ph.D., F.R.S., F.C.S., &c., 

 and H. Wilson Hake, Ph.D., F.C.S., F.I.C. (London: 

 Charles Griffin and Co., 1886.) 



" \ 11 7HY should another hand-book on this subject be 

 * » added to the many which already exist in the 

 language?" In the first paragraph of their preface the 

 authors anticipate the possibility of this question arising 

 in the minds of some chemists, and they therefore answer 

 it by (i) claiming their right, as teachers of lengthened 

 experience, to record their methods of instruction ; and 

 (2) expressing their belief " that the very multiplicity of 

 text-i)Ooks already published tends to show a want felt, 

 but not yet satisfied." 



Their method consist; in first laying down general 

 principles which, when thoroughly mastered, are to be 

 followed up with the facts of descriptive chemistry. 



The introductory chapters containing these general 

 principles, on which the student " with no previous know- 

 ledge of chemistry whatever " is to found his chemical 

 education, comprise about 80 pages of the book, and since 

 the authors lay so much stress on their importance, we 

 cannot pass over this portion of the book without giving 

 a few illustrations of what is to be learnt from the manual 

 apparently intended to supersede all other text-books. 



The representation of a molecule by two small circles 

 surrounded by a larger circle (see note on p. il) may 

 perhaps be mentioned as an instance of the pertinacity 

 with which so many teachers continue to do their best to 

 confuse their pupils with erroneous conceptions of atoms 

 and molecules. 



On p. 36 the melting-point of a substance is incorrectly 

 defined as " the temperature at which it is no longer 

 capable of existing as a solid." On p. 37 it is stated that 

 " most substances increase in volume on melting, but 

 some decrease. In the case of the former the effect of 

 pressure is to lower, in the latter to raise, the melting- 

 point." Thomson proved the opposite of this to be the 

 case. 



The statement generally found in text-books that a 

 ray of light passing from a rarer to a denser medium is 

 refracted towards the perpendicular, and vice versa, is re- 

 produced on p. 42. If the authors are employing the 

 word dense in the optical sense, we think they should say 

 so, if in the ordinary sense, the statement is incorrect. 



On p. 43 they describe total reflection as taking place 

 when " a ray of light proceeding from a denser to a rarer 

 medium strikes the surface, separating the two media at 

 such an angle that the refracted ray would form a right 

 angle (or any greater angle) with the reflected ray." We 

 would like to know the authority for this curious state- 

 ment. 



On pp. 64 and 65 is a table headed " Table of Symbols, 

 Atomic and Molecular Weights, and Valency of the 

 Elements." It contains a list of all the elements, in- 

 cluding those most recently discovered, norwegium 

 amongst the rest, though the existence of the latter metal 

 cannot be said to have been satisfactorily demonstrated. 

 The columns to which we more particularly call attention 

 are, however, those headed "molecular symbol, showing 

 number of atoms in the molecule," and " molecular 



