2 7 8 



NA TURE 



[January 18, 1906 



the method of determining the magnification of an astro- 

 nomical or Galilean telescope by photography. The tele- 

 scope is placed in front of a camera pointed at a distant 

 object (a church spire), and measurements of the telephoto- 

 graph thus obtained, as compared with the picture obtained 

 with thi' camera alone, give (he magnification. 



Of the manv important topics discussed in the Economic 

 Journal for December, 1905, we find a note of eight pages 

 on political economy in Germany, by Prof. G. Cohn, of 

 Gottingen. In it we learn that thirty or forty years ago 

 there were two schools of political economy, namely, on 

 the one hand, the Free Traders, whose science was con- 

 fined to a few very elementary principles and who 

 appealed to the people, and, on the other hand, the 

 economic teaching of the universities. At the present 

 nine the universities, strengthened by the high degree of 

 freedom which their professors enjoy, play an important 

 and ever-increasing part in determining public opinion on 

 economic questions throughout the Empire. Indeed, the 

 author concludes : — " We do not claim too much for our 

 German Political Economy and our German Universities 

 when we say that the spirit which rules them is as wide 

 and many sided as it is a. live and far seeing." 



From the point of view of the disintegration hypothesis 

 of the nature of radio-activity, a brief note by P. G. 

 Costanzo in the BoUctino Mensuale of the Italian Meteor- 

 ological Society (vol. xxiv., p. 25) is of interest; it is stated 

 lal lavas and solid deposits from Vesuvius and the 

 solfatara of Pozzuoli which, on examination, were found 

 not to exhibit any sign of radio-activity were equally 

 destitute of any trace of helium. 



For his inaugural address, delivered on November 22 

 of last year, Prof. R. Threlfall, as chairman of the 

 Birmingham section of the Institution of Electrical 

 Engineers, chose the subject " Some Problems of Electro- 

 and Electrothermal Chemistry." The principal question 

 dealt with was the conversion of carbon into the " non- 

 conducting " variety, and Ludwig's recent attempts to pro- 

 duce diamonds on the large scale were discussed, principally 

 by considering theoretically the probable conditions govern- 

 ing the inter-conversion of the various forms of carbon. 

 Other subjects touched upon included the fixation of 

 atmospheric nitrogen, the ionic theory, and the use of 

 osmium and tantalum in incandescent lamps. 



The final number (No. 7) of the second volume of the 

 Central, the magazine of the Old Students' Association of 

 the Central Technical College, well maintains the high 

 level of its predecessors. It contains a photogravure of 

 Prof. Ayrton, president of the association, whilst a special 

 feature is the large number of photographs illustrating the 

 articles contained in it. Of these articles we may mention 

 an interesting account by Mr. A. A. Barnes of the work 

 recently carried out in excluding the Nile from two of its 

 three channels at Ashmant for purposes of land reclam- 

 ation ; a summary by Prof. Armstrong of the various re- 

 searches made on camphor at the college during the past 

 twenty years, indicating the widely ramified growth of 

 tin problem ; and a description of several types of electro- 

 magnetic ore crushers by Mr. C. J. Guttmann. Two 

 photographs of a new camphor-model illustrate Prof. 

 Armstrong's article. 



A brief note by F. Giolitti in the Gazzetta (vol. xxxv. 

 p. 1S1) contains some interesting particulars with regard 

 to the coagulation of colloidal solutions of ferric hydroxide, 

 the observations forming an extension of the earlier ones 

 of Pean de St. Gilles. Whereas a trace of any polybasic 

 NO. I89O, VOL. 73] 



acid, for example sulphuric acid, added to the colloidal 

 solution obtained by boiling ferric acetate with water 

 instantly precipitates a flocculent " hydrogel " which is 

 insoluble in water, a considerable quantity of a monobasic 

 acid such as nitric acid has to be added to the colloidal 

 solution before a precipitate is produced. The product in 

 this case is a reddish powder which re-dissolves in pure 

 water, and is hence a " solid hydrosol." The quantity of 

 monobasic acid necessary for complete precipitation of the 

 solid hydrosol appears to be fairly definite for a definite 

 set of conditions. The character of the colloidal solutions 

 ol 1 substance, however, seems to depend very largely on 

 the way in which they tire prepared. Thus a solution of 

 ferric hydroxide prepared by dialysis according to Graham's 

 method gives on coagulation very different restdts from 

 those obtained with the solution prepared from ferric 

 acetate. Moreover, other colloidal solutions, such as those 

 prepared from ammonium uranate, plumbic acid, and silicic 

 acid, have certain features which characterise their coagula- 

 tion. It seems necessary, indeed, in considering the 

 general question of colloidal solution, to recognise that 

 several distinct types of coagulation exist. 



The adhesion of electrical contacts in delicate seismo- 

 scopes continues to exercise the minds of Italian 

 seismologists. No other form of seismoscope can be made 

 so sensitive as one which records electrically, but the force 

 tending to separate the contacts is so small that the circuit 

 sometimes remains closed. In the concluding number of 

 vol. x. of the BoUctino della Societa Sismologica Italiana 

 Dr. Agamennone reviews all the devices which have been 

 proposed to overcome the adhesion, and concludes that the 

 only efficient one is that suggested by Dr. T. Alippi, of 

 attaching a vibrator to the seismoscope, which shall act 

 like the decoherer in wireless telegraphy, but adds that his 

 experience in the observatory at Rocca di Papa shows the 

 necessity of carefully adjusting the energy of this vibrator. 

 If too energetic it may produce the very evil it is designed 

 to cure. 



The annual report of the Iowa Geological Survey has 

 just been published at Des Moines under the able editor- 

 ship of Dr. F. A. Wilder, the State geologist. It deals 

 with the year 1904, and forms a handsome quarto volume 

 of 560 pages with 10 folding coloured geological maps of 

 counties, 7 plates, and 51 illustrations in the text. In 

 addition to the State mineral statistics for 1904, and re- 

 ports on the geology of Benton, Emmet, Palo Alto, Poca- 

 hontas, Jasper, Clinton, and Fayette counties, the volume 

 contains an important report on the Portland cement in- 

 dustry and Iowa's natural resources with reference to that 

 material by Mr. E. C. Eckel .mil Mr. II. F. Bain. The 

 report shows plainly that the limestones and clays of Iowa 

 are well suited for the careful study of the cement manu- 

 factures. Despite the large amount of material available 

 and the convenient fuel and transportation facilities, no 

 Portland cement plants have yet been established in Iowa, 

 although a number are in operation in adjacent States. 



We have received from the Home Office an advance 

 proof, subject to correction, of the statement of fatal 

 accidents and deaths in and about the mines and quarries 

 of the United Kingdom during 1905. The total separate 

 fatal accidents were 955 in collieries, 41 in metalliferous 

 mines, and 94 in quarries. 



Mi;. William Heinemann has in hand, under the title 

 of "A Handbook of Metabolism," an English translation 

 of the second German edition of von Noorden's " I.ehr- 

 buch des Stoffwechsels," edited by Dr. Walker Hall, of 

 Manchester. 



