132 



NATURE 



[December 8, 1904 



years 1898-1903, he has constructed approximate isotherms 

 between 50° and 80° S. latitude, and thus made an important 

 addition to the valuable yearly isothermal charts published 

 in Dr. Hann's " Handbook of Meteorology." L>r. Hann's 

 southernmost isobar is 4° C, just below Tierra del Fuego ; 

 Mr. Krebs continues the isotherms for each 4° C. as far as 

 — 16°, which runs near the 70th parallel between longitude 

 60° E. and 60° W. He also draws portions of the isotherm 

 of -20° C, reaching nearly to the Soth parallel. 



The Times of November 29 contains an interesting article 

 on London fogs ; although it deals principally with the most 

 elementary physics of the atmosphere, and with the part 

 played by aqueous vapour, the subject is very ably handled 

 and is made both attractive and instructive. The author 

 points out the well known facts that the amount of invisible 

 vapour in the air varies directly with the temperature ; 

 by whatever process the cooling of the air takes place, the 

 capacity of the vapour to remain invisible diminishes until 

 the " dew point " or " saturation point " is reached; any 

 further cooling produces cloud or fog. He states that it is 

 more than twenty years since it was shown that the vapour 

 molecules cannot of themselves combine to form cloud or 

 fog particles, but that solid nuclei of dust, or other impuri- 

 ties, are necessary, on which the vapour molecules can 

 condense. Taking this for granted, it is seen at once why 

 fogs in London (or other large towns) are so much denser 

 than in the open country. For instance, at an elevation 

 of 6000 feet, say on the Alps, the number of dust 

 particles per cubic centimetre may amount to less than 

 200, while in towns the number may reach 100,000 or 

 200,000. The vapour in the country, condensed on a few 

 particles of dust, will result in a coarse grained form of 

 condensation, whereas in town the same quantity of vapour 

 being distributed over a very large number of dust particles, 

 there results a fine grained fog. The author points 

 out that it is not the large-sized visible dust that does 

 the damage, but the infinitely small, ultra-microscopic 

 particles produced by combustion of fuel and light ; 

 that, in fact, e.\periments have shown that it is possible 

 for cloudy condensation to take place in the absence 

 of dust. In 1897 {Trans. Roy. Soc. Edin., vol. xxxix.) 

 Mr. Aitken stated that dust particles are not absolutely 

 essential for the production of fog, but that, as the air is 

 full of dust and condensation takes place on these by pre- 

 ference, therefore practically all our cloud particles have 

 dust nuclei. The author concludes, justly, we are afraid, 

 that London will always be liable to fogs, owing to its 

 situation and meteorological conditions ; all that can be 

 hoped for is a reduction in the more disagreeable con- 

 stituent elements ; there seems to be, so far, no way of 

 appreciably reducing their frequency or their bad effects. 

 We hope that the experiments begun by Sir Oliver Lodge, 

 with a view to their possible ultimate dissipation by elec- 

 tricity, will be energetically continued. 



The Revue Scientifique (Nos. 20 and 21), in continuing 

 its inquiries as to the existence of the n-rays, publishes a 

 letter from M. Blondlot stating that the photographic ex- 

 posures, the results of which he considers prove the reality 

 of these radiations, were made by a laboratory assistant who 

 was ignorant of the effects he ought to obtain, and was 

 therefore not unconsciously biassed. The obvious rejoinder 

 is made that the results obtained in this way are less to be 

 trusted than if they were due to M. Blondlot himself. M. 

 Lambert claims that his experiments showing that the n-rays 

 exist were made in a manner excluding subjective pheno- 

 mena. On the other hand, MM. Cailletet, Lippmann, 

 NO. 1832, VOL. 71] 



Berget, Turpain, and Perrin have all failed to obtain experi- 

 mental proof of their existence. 



P.iRT X. of the Transactions of the Royal Dublin Society 

 contains a continuation of the researches of Messrs. W. F. 

 Barrett, W. Brown, and R. A. Hadfield on the physical 

 properties of a series of alloys of iron. It is shown that a 

 remarkable similarity exists between the diminution of the 

 electrical conductivity and the change in the thermal con- 

 ductivity of iron, which are caused by the addition of other 

 elements. Not only is the general order of the electrical 

 and thermal conductivities the same for all the alloys, but 

 equal increments of any given element appear to produce 

 a corresponding diminution of conductivity for both heat 

 and electricity. It is remarkable that the effect of alloy- 

 ing iron with another element, even a better conductor, is 

 always to reduce both the thermal and the electrical con- 

 ductivities. The ratio of the two conductivities is, how- 

 ever, not exactly the same for all alloys ; on plotting the 

 electrical against the thermal conductivity, a fairly smooth 

 parabolic curve is obtained showing that the ratio increases 

 in magnitude as the conductivity of the alloys increases. 



The October part of the Physical Review contains an 

 account by Messrs. C. W. Waidner and G. K. Burgess of 

 a number of measurements which they have made by photo- 

 metric methods of the temperature of the electric arc. 

 Wien's law of the distribution of energy in the spectrum 

 was assumed as a basis of calculation, and three distinct 

 types of photometers, namely, those of Holborn and Kurl- 

 baum, of Wanner, and of Le Chatelier, were employed. 

 The values obtained for the " black body " temperature of 

 an arc of pure graphite by the three methods agreed within 

 30° C, the average being about 3700° abs. The true 

 temperature of the arc must be higher than this by an 

 amount depending on the departure of the radiation from 

 true " black body " radiation, and may possibly be between 

 3900° and 4000° absolute. Contrary to the usually 

 accepted view, the temperature of the arc does not appear 

 to be independent of the current, and it is undoubtedly 

 influenced by the degree of purity of the carbons forming 

 the arc. With impure carbons, the temperature is lower 

 by 40° C. than in an arc of highly purified graphite. Such 

 variations would appear to preclude the suggested use of 

 the brightest part of the positive carbon of the electric arc 

 as a standard source of light. 



The second number of the Extensionist, which is a record 

 of the University Extension Guild, has reached us. In 

 addition to numerous descriptive notes on the work of the 

 guild, this issue contains addresses by Sir Arthur Riicker, 

 F.R.S., Mr. Hilaire Belloc, and Mr. Banister Fletcher. 



The Infants' Health Society has published a pamphlet 

 entitled " The Present Conditions of Infant Life, and their 

 Effect on the Nation," which directs attention to the almost 

 complete failure of our present method of rearing the infants 

 of the working class. In the poorer parts of the larger 

 towns and cities it is not uncommon for nearly half the 

 children born to die in infancy. The dominating cause of 

 this appalling mortality is the improper feeding of the 

 infant. 



Messrs. A. and C. Black have published the 1905 issues 

 of three useful annuals — " Who's Who," " Who's Who 

 Yearbook," and the " Englishwoman's Yearbook." 

 " Who's Who " has been enlarged again this year, nearly 

 a hundred pages having been added, bringing the total up 

 to 1796. Due prominence is given to men of science and 

 their work, not only of those in this country, but in other 

 parts of the world. There is a want of uniformity in the 



