246 



NA TURE 



[January 16, 1908 



oxides and hydrides, acids, bases and salts, lialogen 

 compounds and sulphides. 



The preparation of the nitrides of calcium and boron 

 strikes us as strange. The calcium or boron are 

 heated in the air, and so one obtains a mixture of 

 o.xide and nitride. As, however, the o.xide and nitride 

 cannot be separated, there seems very little point in 

 the experiment, except that the student's attention is 

 directed to ammonia from the air. Certainly, but if the 

 air is first passed over red-hot copper, thvis freed from 

 o.xygen, and subsequently passed over the heated cal- 

 cium or boron, surely the experiment is much more 

 striking, and, further, the pure nitride is prepared. 

 This method of preparation would also lead up to a 

 discussion of argon and similar gases. 



The book will undoubtedly be of great use to 

 teschcrs of inorganic chemistry and others who wish 

 to study the subject from a preparatory point of view, 

 but it is rather too full for the average student, who 

 would certainly require very careful direction, or he 

 would be inclined to wander along in a rather aimless 

 fashion. ' F. M. P. 



'The Bacteriological Examination of Disinfectants. By 

 William Partridge. With a preface by Major C. E. P. 

 Fowler. Pp. 66. (London : The Sanitary Publish- 

 ing Co., Ltd., 1907.) Price 2S. 6d. net. 

 The subject of disinfectants has lately attracted con- 

 siderable attention, and Mr. Partridge's little book 

 forms a very useful summary of the methods employed 

 for testing bactcriologically the germicidal value of 

 disinfectants. The Rideal- Walker or " drop " method 

 is rightly that most favoured, and the major part of 

 the book is devoted to it. We doubt if the explanation 

 given on p. 17, that a forty-eight hours' culture of 

 B. typhosus is less readily killed by a disinfectant 

 than a twenty-four hours' one, because it is more 

 vigorous, is correct; we should ascribe the fact rather 

 to the greater number of bacilli and to clumping in 

 the older culture. On p. t8 it is said that while a 

 broth having a reaction of -f-i'S is suitable for the 

 culture of the typhoid bacillus, for the diphtheria and 

 cholera organisms a " neutral or alkaline broth must 

 be substituted." The broth named is quite suitable 

 for these organisms, for it is alkaline in the ordinary 

 acceptation of the term ; though acid to phenolph- 

 thalein, it is still alkaline to litmus. On p. 34 an experi- 

 ment is quoted to show that an organism from different 

 sources may have a different resisting power from a 

 disinfectant. Doubtless this is so, but the experiment 

 does not prove it. The experiment shows that two 

 strains of the typhoid bacillus, with strengths of car- 

 bolic of I in 70 and i in 100 respectively, are killed 

 in between 5 and 7^ minutes; obviously the one might 

 have been killed in 55 minutes, the other in 7j minutes, 

 and actually there might have been little difference 

 between them. Everyone has his own method of mani- 

 pulating tubes for inoculation, but we do not like either 

 method depicted in Figs. 3 and 4. Major Fowler, 

 R.A.M.C., contributes a useful introduction. 



R. T. Hewlett. 



Ergcbnissc iind Forlschrittc dcr Zoologie. Edited bv 

 Dr. J. W. Spengel. \'ol. i., jiart i. (Jena : Gustav 

 Fischer.) 

 Under the above, title Mr. Guslav Fisclier is issuing 

 a new zoological journal, of which a variable number 

 of parts are to appear each year, the whole to form 

 an annual volume at the price of sixtv marks. As 

 no prospectus is issued with the part now before us, 

 we are unable to indicate the ground which the publi- 

 cation is specially intended to cover. The present part 

 contains 23S somewhat closely printed 8vo pages, illus- 

 trated by tlflv text-figures; and from this we presume 

 that plates do not enter into the scheme of the new 



NO 1994. ^'OI • 77I 



venture. The name of t'no editor is a sufficient 

 guarantee that only papers of a high order will be 

 accepted for publication, this being fully borne out by 

 the contents of the initial number. These comprise a 

 discussion on chromosomes by Mr. Valentin Hacker, 

 of .Stuttgart; an article by Dr. Richard Heymons on 

 the various types of insect metamorphosis, and their 

 relation to the metamorphoses of other arthropods ; 

 and another, by Mr. O. Maas, of Munich, on the 

 scyphomedusae. The new enterprise has our best 

 wishes for success. R. L. 



LETTERS TO THE EDITOR. 

 [The 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 talien of anonymous communications.] 



Seismographs and Seismograms. 



.As I have had occasion to study and compare the recordri 

 of nearly all the types of seismographs for recording 

 distant earthquakes which are now in use, I may perhaps 

 be permitted to add something to Prof. Milne's letter in 

 N.4TURE of January 2. The nature of the records, and the 

 relative merits of different types, of seismographs, are not 

 generally apprehended in England, and appear to be mis- 

 understood in Strassburg, from whence much of the recent 

 seismological literature has been inspired. 



The two leading problems of seismology, as it stands 

 at present, are the determination, firstly, of the exact 

 nature and amount of the movement which takes place, 

 and, secondly, of ihe time requisite for the transmission 

 of the different types of disturbance from the origin, to 

 various distances, and in various directions, through tht- 

 earth, or along its surface. The first of these is naturally 

 the special object of purely seismological stations and 

 observatories, and for it no single instrument or type of 

 instrument will be sufficient. From the mathematical and 

 experimental investigations of the mechanics of seismo- 

 graphs by Prince Galitzin, Prof. Rudzki and others, it 

 has been conclusively established that no form of instru- 

 ment, having a pendular period of vibration of its own, 

 however perfectly the oscillations may be damped, can 

 possibly record with exactitude an undulatory movement 

 of the soil such as is caused by earthquakes. -As every 

 instrument giving a continuous record must necessarily 

 be of the nature of a pendulum of some sort or other, 

 owing to the necessity for bringing the recording point 

 back to the zero line of the record, it is obvious that no 

 single instrument can suflice for this purpose, and thai 

 the only way, bv which an understanding of the nature 

 of the movement of the soil can be arrived at, is by 

 Installing a number of instruments, of different types and 

 var\ing response to movements in diverse directions and 

 of unlike period. 



For the second purpose a totally different set of con- 

 ditions comes In. It Is no longer necessary to attempt 

 an exact, or even an approximate, representation of the 

 actual movement of the ground, so long as the instru- 

 ments give records in which the different phases of wave 

 motion can be recognised with reasonable certainty ; but. 

 since the solution of this problem Involves the collection of 

 numerous records from many stations, it is necessary to 

 obtain the cooperation of astronomical, physical, meteor- 

 ological, and other observatories, and, consequently, 

 certain conditions, which may be ignored in a specially 

 seismological station, have to be taken into consideration. 

 These are : — 



(i) The instrument must not be unduly cumbrous or 

 bulky ; it must be easy of transport, occupy only a 

 moderate floor space, and not require special and expensive 

 foundations. 



(2) It must run without much attention, and at as 

 moderate a cost as possible. 



(3) It must be sufliriently sensitive and consistent in its 

 action to give records capable of Interpretation as a general 



