Septemiskr 7, 1905] 



NA TURE 



455 



admitted that this conclusion needs confirmation from 

 future discoveries before it can be definitely accepted. 

 The specimens on which the new genera Cory- 

 phaenopsis and Bayeria (Fritsch) are founded are 

 certainly remarkable. 



Dr. Fritsch'." section of the work shows that all 

 the usual groups of Cretaceous Reptilia are repre- 

 sented in the Bohemian rocks. There are undoubted 

 fragments of Plesiosaurs, and there is one interest- 

 ing brain-cast which the author describes as probably 

 referable to Polyptychodon. Dr. Fritsch. however, 

 overlooks the fact that the skull of Polyptychodon is 

 actually known in England, and is undoubtedly 

 Plesio.saurian or Pliosaurian, not Mosasaurian. 

 Chelonian remains occur, evidently representing 

 turtles related to the small Chelone Beiistedi from the 

 English Chalk. Some fragments appear to be 

 Mosasaurian, but those described under the new name 

 of Iserosatirus litoralis are e.xtremely problematical. 

 Other fragments, ascribed without much reason to 

 Dinosauria, scarcely suffice to justify the new names 

 bestowed on them. Some good new figures of the 

 interesting wing-bones of the small Pterodactyl, 

 Ornithocheirus hlavaci, are given, and the volume 

 concludes with a systematic list of species. 



A. S. W. 



Die Bedeiitung des Experimentes fiir den Unterricht 

 in der Chemie. By Dr. Max Wehner. Pp. 62. 

 (Leipzig and Berlin : B. G. Teubner, 1905.) Price 

 1.40 marks. 

 This brochure forms part of a " Sammlung natur- 

 wissenschaftlich-piidogogischer Abhandlungen," and 

 is very hard reading for an ordinary English chemist. 

 It is divided into tw-o parts, the first of which deals 

 with the importance of experiment for attaining 

 the object of chemical instruction, and the second 

 with the importance of experiment in relation to 

 method in chemical instruction. It is hard reading 

 in the sense that one has to wade through detailed 

 arguments which culminate in conclusions such as 

 " description does not suffice for the instruction of 

 the pupil in chemical processes," and "the develop- 

 ment of the laws concerning chemical processes from 

 e.xperimental observations is more effective for 

 chemical teaching than their deduction from quoted 

 examples." The work is, in fact, an example of pure 

 pedagogical exercitation, and it may be recommended 

 with confidence only to those who have a liking for 

 that kind of literature. \. S. 



Monographie des Cynipides d'Eiirope et d'Algerie. 

 By I'Abb^ J. J. Kieffer. Tome second. 2me. fasci- 

 cule. Pp. 289-748; plates ix-xxi. (Paris: A. 

 Hermann.) Price i8s. 

 This is the conclusion of vol. vii. bis of Andrd's great 

 series of monographs, " Species des Hymenoptferes," 

 and completes the Cynipides, or gall flies. The pre- 

 vious portions have already been noticed in Nature 

 (vol. Ixvii. pp. 124-5, December 11, 1902, and vol 

 Ixviii. p. 221, July 9, 1903), and the part now pub- 

 lished completes the Cynipides, 5e tribu, FigitinEe ; 

 and also includes the Evaniides (divided into two 

 tribes, Evaniinse and Gasteruptioninae), the Ste- 

 phanides, Trigonalides, Agriotypides, generaf supple- 

 ments, a " Catalogue mdthodique et synonymique," 

 extending from pp. 653 to 741 (double columns), and 

 general indices. 



The plan of the work is uniform throughout, and 

 as the previous portions have already been discussed 

 at considerable length, an extended notice is here 

 unnecessarv. W. F. K. 



NO. 1S7I, VOL. 72] 



The Gum-Bichromate Process. By J. Cruwys 

 Richards. Pp. 119. (London : Iliffe and Sons, 

 Ltd., n.d.) Price 2S. 6d. net. 

 This process of photographic printing is about fifty 

 years old, but it is only during the last ten years or 

 so that it has been adopted for practical purposes. 

 When first introduced it was deliberately rejected, 

 because it was not equal to the then known processes 

 in reproducing the detail of the negative ; latterly it 

 has been taken up and very much appreciated by 

 some of those who desire to be able to alter or 

 " control " their photographic printing, and so obtain 

 results that, while they can lay no claim to mechanical 

 accuracy, more nearly please the aesthetic taste of 

 the worker. At the present time there are more 

 methods of photographic printing than there were 

 a generation ago that are excellently adapted for the 

 purposes of photography pure and simple ; therefore 

 the gum-bichromate process is still more than it was 

 then a process for the specialist in the direction named. 

 The author of this volume is well known as a 

 successful worker of the method. He gives his own 

 formulas, and states clearly the practical details that 

 he prefers to follow, but he also describes the methods 

 of others. He is a warm advocate of " multiple 

 printing"; that is, after coating the paper, exposing, 

 developing with warm water aided with a brush or 

 by other mechanical means, coating, exposing, and 

 developing a second or even a third or more times, 

 so gradually building up the picture with the maxi- 

 mum opportunity of "control." It will be obvious 

 that every possibility of improvement in the hands of 

 the skilful is a probability of error in the hands of 

 the artistically ignorant, and that the process does not 

 claim attention from a photographic point of view at 

 all, but as enabling an artist to express his ideas with 

 less trouble and perhaps with more accurate drawing 

 than if he worked wholly by hand. The volume in- 

 cludes several reproductions of the author's works, 

 some of them showing the print in its various stages 

 of evolution. 



LETTERS TO THE EDITOR. 



[I'he 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 intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.] 



Recent Changes in Vesuvius. 

 I BEG to enclose a somewhat free translation of a letter 

 I have recently received from Prof. G. Mercalli, of Naples, 

 concerning certain changes which have taken place in 

 Vesuvius this year. During a visit to the mountain on 

 .August 14-16, I was able to approach quite near to the 

 sources of the lava streams described by him, and also to 

 examine the remarkable tunnels formed at certain places 

 by the cooled surface of lava streams which had sub- 

 sequently diminished in volume, or had even " run dry." 



During the week preceding my visit, many incandescent 

 bombs of pasty rock had been ejected from the crater at 

 the summit, mostly in the direction of the side facing 

 Pompeii, and these successively rolling down the ash-slope 

 presented a beautiful spectacle at times. The lava streams 

 proper often presented that curious double appearance, due 

 to the fact that the colder and darker scorire, floating 

 down the stream, keep to the more swiftly-moving current 

 in mid-stream, and avoid the sides. 



Yesternight (August 20) but one of the lava streams 

 referred to by Prof. Mercalli was visible from Naples, the 

 other having apparently ceased. 



The explosions of Stromboli are occurring at intervals 

 of about 3J minutes. R. T. GOnther. 



R.M.S. Oroya, off Stromboli, August 21. 



