July 12, 1883] 



NA TURE 



243 



The descriptions of the thymus and thyroid glands 

 appear to have been transposed. 



The three divisions of the cloaca are not described, and 

 the rudimentary right oviduct is not mentioned, though 

 the "Fallopian tubes" are said to open into the cloaca. 



It is a mistake to introduce questionable homologies 

 into a book of this kind, especially when they are unsup- 

 ported by fact. Thus the statement in § 118 that the 

 "thin sheet of muscle which is closely adapted to the 

 concave ventral surface of the lungs . . . represents the 

 diaphragm of mammals," is certainly misleading. In 

 the first place, the position and relations of these muscles 

 are entirely different from those of the mammalian dia- 

 phragm, and, moreover, they receive their nerve-supply 

 from the intercostals, the phrenic being absent. The fact 

 that the phrenic arises so far forwards appears to indicate 

 an entirely different origin for these two structures. 



With these slight exceptions, however, the descriptions 

 and directions leave little to be desired for clearness and 

 accuracy. It is certain that accurate detailed directions 

 are far more valuable for elementary teaching than more 

 general ones ; the student, once having mastered them, 

 finds little difficulty in grasping the wider bearings of the 

 subject. Such works as the present, therefore, which 

 entail a careful examination of every point mentioned, 

 not only save both student and demonstrator much 

 trouble, but insure more accuracy in work. A series of 

 pamphlets such as the authors intend to publish, treating 

 of all the more important vertebrate types usually dis- 

 sected in an ordinary course on comparative anatomy, will 

 certainly prove most valuable. 



An Easy Introduction to Chemistry, Edited by the Rev. 

 Arthur Rigg, M.A., and Walter T. Goolden, M.A. 

 New Edition Revised, pp. 148. (London : Rivingtons, 

 1883.) 



This book is based on a " First Book of Chemistry," by 

 Dr. Worthington Hooker, and is intended, we are told in 

 the preface, " to convey information in respect to changes 

 which are likely to attract the attention of young persons 

 who observe and inquire." 



It is questionable whether " young persons" do well in 

 attempting to study chemistry ; the chemical laboratory 

 is not a place in every way suited to the requirements of 

 youth, but without steady work in a laboratory no real 

 progress in chemistry can be looked for. Should, however, 

 any youth desire information regarding material changes 

 which he observes around him, he will find a considerable 

 amount of information in this little book ; but should he 

 be desirous to study chemistry, he will not we are afraid 

 derive much assistance from this " Easy Introduction." 

 Many experiments are described and numerous well- 

 executed illustrations are given, but several of these ex- 

 periments could not be performed by a beginner without 

 the aid of a teacher or of much more detailed description 

 than is given in the text. To read statements of the 

 results of experin.ents is not the way by which young 

 persons can acquire interest in or a knowledge of 

 chemistry. 



Although excellent in many ways, yet we cannot think 

 this book will prove an efficient introduction to chemistry ; 

 a perusal of it may, however, serve to stimulate young 

 persons to seek for an introduction to the science, some 

 of the materials for the construction of which are put 

 before them in this work. 



Practical Electric Lighting. By A. Bromley Holmes, 

 Assoc. Inst. C.E. Sixty-two Illustrations. (London: 

 E. and F. N. Spon, 1883.) 



It is with pleasure that we shall watch the success of Mr. 

 Holmes's little book on " Practical Electric Lighting.'' 

 Mr. Holmes has clearly and simply put before the un- 

 electrical public as much and no more of theoretical elec- 

 • tricity as is necessary for his purpose, together with a 



good general summary of the chief machines and appli- 

 ances in present use. 



Besides this, much useful information is given in the 

 last two chapters, first, on the present economic state of 

 electric lighting, and second, on the best means of apply- 

 ing the power to electric machinery. If there be one 

 point in the book not so strong as the rest it is that the 

 descriptions of the dynamos and lamps would have been 

 better if they had entered a little more into detail. 



c. c. s. 



LETTERS TO THE EDITOR 



[Tie Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts, 

 No notice is taken of anonymous communications. 



[ The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible otherwise to insure the appearance even 

 of communications containing interesting and novel facts.\ 



Geology of the Congo 



I have received from one of the Baptist missionaries in the 

 front of the Congo mission a basket of specimens of rocks and a 

 letter giving some particulars of the geological structure of the 

 localities. The letter maybe interesting as the first news of this kind 

 from the centre of Africa, on its western side, and I therefore 

 place it at your service. S. R. Pattison 



S, Lyndhurst Road, Hampstead, N.W., July 7 



Liverpool Station, B.M.S., Stanley Pool, Congo River, 

 S.IK Central Africa, March 15, 1883 



S. R. Pattison, Esq. 



Dear Sir, — Before leaving England in 1879 you made us a 

 kind offer to render us any help in geological and mineralogical 

 matters that lay in your power, and that kindness has been re- 

 called to mind every time I have examined a piece of rock. I 

 had seen such geological variety in the few parts of England that 

 I had visited, that in my ignorance I was expecting to find a 

 much greater variety out here and at least some fossil treasures. 

 But in this, as you may guess, I have been disappointed. 



In sending home some curios the other day, I inclosed a few 

 native ingots of lead and copper, which I thought might interest 

 you. They are "mined" in a district of the Biznnseke tribe 

 called Noama, some twenty-five miles west-north-west of the 

 Ntombo Mataka Falls of the river. I have not visited the place, 

 but I believe de Brazza (concerning whom there have been some 

 paragraphs in the newspapers lately) passed through this 

 "mining district." 



Although I believe that no metal from that part is ever sold 

 to white traders, it is an important item in native trade with the 

 far interior. Some are used to make bullets, others are recast 

 to make anklets, &c. If the district is rich, or there is much 

 silver in the lead, the French will perhaps work there. 



The case of curios was sent away before I had intended. I 

 had hoped to have added other thing--, and a piece of sandstone 

 from the cataracts here. 



Mr. Stanley indirectly hinted that Stanley Pool might be the 

 crater of a volcano (extinct of course) which in old time had rent 

 a rift in the hills, forming an exit to the pent-up waters of a vast 

 interior sea. I am not sure how much of this was made public 

 by him. It was, however, his opinion on our return from our 

 first visit to the Pool. He speaks also of lava reefs, granite, 

 gneiss, trap, &c. 



Dr. Pechuel Losche, late of the German Expedition, which 

 spent some time (about five or six years ago) on the coast about 

 the Kioilo and Chiloango Rivers, was for a short lime in charge 

 of the Belgian expedition here during Mr Stanley's absence. 

 He assures me that there is no trace of igneous action above 

 Isangila at least. There may be traces of such action at the 

 Yelala Falls, which form the first bar to navigation from the sea. 

 Between there and Isangila Falls quartz, slate, micaceous, and 

 granitic (apparently) rocks are the rule. 



Above Isangila limestone is abundant for about ten miles, 

 above that slaty rocks are prevalent. Limestone crops out again 

 about the country of the Basundi. This gives place to a red 

 shale at the western boundary of the Babwende, and at the 

 Ntombo Mataka Falls a red sandstone appears under the shale. 



