NA TURE 



[January 18, 1906 



Lehrbuch der Meteorologie. Second edition. By Prof. 



Julius Hann. Pp. 042. (Leipzig: Herm. Tauch- 



nitz, [905.) Price 24 marks. 

 1\ the yeai 1901 the author of this volume published 

 the first edition, and on its appearance it was uni- 

 versally announced as the " classic " of meteorological 

 literature. The work itself was a veritable mine of 

 information, and the host of reference to original 

 sources made it an absolute necessity for anyone deal- 

 ing with this si ience to have it in his possession. 



We have now before us a second edition. In this 

 the authoi has made considerable alteration. In the 

 first place, the size of the volume, as regards amount 

 of matter it contains, has been very much reduced, a 

 host of original references have been dispensed with, 

 and the subjeel is dealt with in a more brief form. So 

 rapid has been the progress of meteorological science, 

 and so many have been the changes in ideas on numer- 

 ous fundamental issues, that in many places this 

 matter lias had to be completely overhauled. Thus, to 

 take one instance, namely, the investigation of the 

 upper air by means of kites, balloons, and bdllons- 

 sondes, new light lias been thrown on the movements 

 of atmospheric currents, and innumerable data col- 

 lected relating to temperature, pressure, and other 

 el, ments in the higher strata. 



The above is one of many cases where reconstruc- 

 tion has been rigorously carried out. Further, the in- 

 sertion of all this, the latest, material ha- necessitated 

 a great number of new references, so that the pre- 

 sent volume with regard to these may be considered 

 as a supplement to the first. 



Several new and useful tables have been inserted in 

 an appendix, one of these being a table of mean 

 monthly and annual temperatures of 143 places in 

 different parts of the world. 



In the text are eighty-nine figures, nine autotype 

 plates, am] fourteen charts. The get-up of the book 

 is of the same high standard of order as that of the 

 first edition, the paper and printing being all that 

 could be desired. 



The volume should be in the hands of everyone who 

 is in any way interested in meteorology, and is another 

 very valuable addition to our meteorological literature 

 bv the master of the subject. 



The Uses 0} British Plants. By Rev. Prof. G. 

 llenslow. Pp. vi+184. (London: Lovell Reeve 

 and Co., Ltd., 1905.) Price 4s. 6d. net. 

 About forty years ago a book was published on the 

 " Useful Plants ol Great Britain," written by C. P. 

 Johnson and illustrated by J. E. Sovverby. judging 

 from the few copies one meets with, there has 

 not been in the past much demand for information 

 of this nature, but there is some indication of in- 

 creased interest being taken in economic botany. 

 The arrangement adopted by Prof. Henslow, in which 

 he follows the nomenclature and order laid down in 

 Bentham's " British Flora," accompanied, too, by the 

 same set of illustrations, makes this practically a 

 companion volume. Owing to the cost of production 

 or the discovery of better substitutes, several plants 

 once grown in the British Isles for their products 

 have gone out of cultivation ; the dyes produced by 

 Rhamnus, Genista, and Rubia have been superseded 

 by aniline dyes, and very few woad mills remain; one 

 of those still existing was described in Nature, 

 November 12, 1896; nettle-cloth is not likely to be 

 revived unless the term is applied to the material 

 produced from rhea or the Nilgherry nettle, two 

 exotic Urticaceae. Such productions, and the cultiva- 

 tion of certain plants formerly reputed to be effica- 

 cious, are mainly interesting on account of their 



NO. 1890, VOL. 73] 



In inn il association, and with these the author deals 

 sufficiently fully; also he has given a good deal of 

 space to the derivations of the Latin names. On the 

 otber hand, he might have enlarged with advantage 

 in the case of those plants which are still cultivated 

 or which are closely allied to plants of economic value. 

 the bonk is restricted to flowering plants. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can lie undertake 

 l<: 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.] 



Cheirality of Form of Crystals of Epsom Salt. 



In studying the optical behaviour of the optically active 

 biaxial crystals of zinc sulphate (ZnSO,7liX>) and I p om 

 salt (MgSO.^rLO), I found that the rotation (which, the 

 crystal being trimetric, is the same for each optic axis) 

 whs tu the left in all the thirteen crystals that I prepared. 

 1 then turned my attention to the crystalline form, which 

 affords a more rapid means of determination of the 

 cheirality, and is, moreover, applicable to small crystals. 

 In tin case nl Epsom salt, twenty-two crystals were ex- 

 amined ; sixteen of them were found to be positive, six 

 doubtful, while net one was found to be negative. 'the 

 crystal accepted as positive is that of which a diagram is 

 given in Watt's " Dictionary of Chemistry " (vol. ii., 

 p. is", diag. 282, 1S83). In examining the form, the 

 smallest of the faces + P/2 and — P/2 was looked for, 

 ami then considered as belonging to the set of small faces, 

 even if, as occasionally happened, others of the same set 

 were large. The cheirality of form of zinc sulphate 

 crystals is not marked enough to permit of any certainty 

 nl identification. The reason for this constant selection 

 by the substance of a particular one of the two possible 

 forms is perhaps that the crystallisation may have been 



occa 1 il by particles of organic dust that are themselves 



cheiral. H. C. Pocklington. 



Deposits on Telephone Wires. 



At East London, in the Cape Colony, one of the in- 

 habitants recently complained that two telephone wires 

 passing over his roof, an iron one, were seriously injuring 

 it, and asked that they might be removed at once, and 

 the building re-roofed at the cost of the Government. In 

 support of his statements he referred to some lines of a 

 whitish colour on the roof immediately under the wires. 

 Many theories were advanced, one being that the moist 

 sea air laden with salt had condensed on the wires, and 

 that when the moisture had evaporated the salt had been 

 shaken loose by the vibration and fallen on the reel, form- 

 ing in time the lines referred to. The officials on the spot 

 stated that they could taste the salt ; but on some of the de- 

 posit being removed from the roof the iron was found to 

 be quite intact. On the powder being analysed not a 

 trace of salt or of any chloride, soluble or insoluble, could 

 be found, and the result of the analysis showed the deposit 

 to be nothing but silica, with very faint traces of iron ami 

 lime. The sand, a fine powder, must have been blown on 

 to the wires when they were damp, and on evaporation of 

 the moisture taking place have fallen on the roof owing 

 to the vibration of the wires. 



A Subscriber. 



Sounding Stones. 



ArROPOS of Mr. Tingle's letter of last week, it may be 

 of interest to note that fairly good specimens of " sounding 

 stones " occur at Corick, on the borders of the barony 

 of Erris, co. Mayo. The bridge at this village is known 

 as the " musical bridge," from the fact that stones which 

 form the coping of the parapet give out a musical note 

 when struck with a piece of stone or metal. 



T. Dillon. 



Ballina, co. Mayo, January 8. 



