294 



NA TURE 



[July 26, 1S94 



of the important results that may be expected from a 

 complete discussion. Hut the author is more intent upon 

 describing the general effects of wind circulation as 

 affected by the rotation of the earth, before proceeding to 

 partial and local disturbances. Of course, in this section, 

 the author follows Ferrel, and without employing mathe- 

 matical illustration, succeeds in fairly well placing before 

 the student an outline of the essential features that mark 

 the work of his distinguished countryman. 



This gradual progress of the book seems to throw the 

 question of rain and precipitation far into the work. No 

 inconvenience arises from this, though in many minds, 

 not necessarily scientific, the subject of rain is considered 

 the most important factinconnection with meteorological 

 science. Prof. Davis, however, is not to be hurried. He 

 wishes to approach the subject of cyclones and local 

 storms, and as these are more or less accompanied with 

 rainfall, he finds it necessary, in pursuance of his scheme, 

 to clear away the general features connected with the 

 moisture of the atmosphere, including clouds, dew, frost, 

 and the various forms in which we find water precipitated. 

 In connection with cloud observation, a simple method is 

 mentioned of determining the direction and velocity of 

 cloud movement, which might be worthy of more syste- 

 matic trial than, it is believed, has yet been accorded to 

 it. The method consists in noting the path of the reflec- 

 tion of a cloud in a horizontal mirror, in which the 

 observer looks through an eye-piece that remains fixed 

 during the observation. If the eye-piece is placed so that 

 the reflection of a certain part of the cloud falls at the 

 centre of the mirror, and after a few seconds a radial 

 arm is turned so as to bring its edge on the position then 

 taken by the cloud, the edge ol the arm will lie parallel 

 to the cloud's motion, on the admissible assumption that 

 the cloud is drifting in a horizontal plane, (pp. 181-2.) A 

 slight addition to the apparatus permits the ready appre- 

 ciation of the relative velocity of the cloud drift, far 

 better than can be estimated by the eye alone. 



Having dealt with the general subject of rain and 

 clouds, the author is in a position to treat of cyclonic 

 storms, thunderstorms and tornadoes, and the more 

 violent interruptions of meteorological phenomena. The 

 reason for this section, interesting as it is, being sand- 

 wiched in between the description of clouds, &c., and 

 the causes and distribution of rainfall is, however, not so 

 clear. The author probably did not wish to have a 

 greater separation than possible between his chapter on 

 winds and that on cyclones; but we think it would have 

 been better to have finished the subject of rainfall before 

 returning to the motion of the atmosphere. But the writer 

 is clearing the way for the consideration of the " weather," 

 " weather prediction," and climate, with which his book 

 ends. On the subject of weather forecasts, Prof. Davis 

 does not take a very hopeful view. We believe that our 

 authorities at Victoria Street look with a certain degree 

 of satisfaction on the results of their predictions. They 

 are able to point to a percentage of some yo per cent, 

 of successes, and as far as is known, they, and the public 

 too, consider their existence justified, liut listen to Prof. 

 Davis : — "The number of stations has grown, and their 

 equipment has been materially improved; the accuracy 

 of various processes preparatory to charting has been 

 increased ; a vast body of information has been accu- 

 NO. I 291, VOL. 50] 



mulated for study relative to the kinds and changes of 

 weather ; various predicting officers have had extended 

 practice in their art, and while the forecasts are truly 

 made for longer periods than they were at first, and are 

 certainly superior in definiteness and accuracy to those 

 issued twenty years ago, their improvement is not so 

 great as was hoped for. Mistakes in prediction are still 

 made, and of much the same kind as at the beginning of 

 the service." (p. 325.) 



In laying aside this book, which we have read with ., 

 pleasure, and heartily commend to the student, one word of '' 

 caution may not be unnecessary to the English reader. 

 The book is written for American students, and the use 

 of "our " and " us" is apt to be a little confusing. For 11 

 instance, "our" damp winter north-easters (p. 145) will 1 

 scarcely apply to "our" climate, and the statement 

 (p. 269) "that in the sixyears 1S85-1S90 there were 2233 

 buildings set on fire by lightning in this country," is one 

 which must be considered in connection with the area of 

 the country to which it applies. W. E. P. 



THE WEALDEN FLORA. 

 Catalogue of the Mesosoic Plants in the Department of 

 Geology, British Museum. Part I. Thallopliyta— 

 Pteridophyta. By A. C. Seward, M.A., F.G.S. 

 (London : Printed by order of the Trustees, 1894..) 



THIS hand-book serves to show how interesting a 

 monograph of all that is known regarding this li 

 mysterious formation would prove. In the folds of the 

 Wealden we imagine the secret of the evolution ol 

 angiosperms must be locked. It is as if we stood at the 

 mouth of a great river flowing from an unexploreil 

 interior, whose flotsam we anxiously interrogate for clues 

 as to the nature of the unknown hinterland ; yet nothing 

 reaches us from beyond the coast-belt, which we have 

 already explored. The Weaklen flora is in fact so 

 meagre that it is hard to regard the formation as 

 fluviatile, and one is tempted to believe that it was 

 formed in some brackish lake into which the spoils of 

 the land were rarely drifted. 



The first pages afford a comparison of the plants of 

 the English Wealden with those of other countries, but 

 that any of the formations included, especially from 

 beyond Western Europe, are really contemporaneous, 

 must be open to doubt. None of them, however, with 

 trifling exceptions, contain any indications of the 

 presence of angiosperms. Another remarkable fact is 

 the extraordinary geographical range of the English 

 species, only ten out of thirty being peculiar to this 

 country, and these are the most poorly represented. \ 

 perhaps unavoidable drawback, to this book and former 

 ones of the series, is that they change established nomen- 

 clature so greatly as to render preceding lists of British 

 fossils useless. 



A new term, Algiles, designates the markings which 

 probably represent Alga:. A rather widely distributed 

 Cliiira and a new species under Marchtntitcs are 

 important acquisitions ; as are the three species of 

 Equisctum with tuberous roots, of which one is new. 

 These tubers show that some description of fruit could 

 have been preserved if they had ever been present. 



The bulk of the volume is taken up with the Ferns, 

 which are fairly, perhaps ovcrcautiously, treated. The 



