344 



NATURE 



[May 12, 1921 



formerly plentiful in the Fens, but destroyed by 

 drainage operations. During the same period our 

 flora has been augmented by a number of emigrants 

 from other countries which have become more or less 

 completely established. The dubious plants of Britain 

 — that is to say, plants which have been reported as 

 British — make a very long list. Some are mere 

 casuals, many have been wrongly identified, and some, 

 it is to be feared, were wilful impositions. The prob- 

 ability is that the majority were really erroneous, but 

 Dr. Druce suggests that the publication of these records 

 in an easily consumable form may, by directing atten- 

 tion to them, lead to one or two being re-discovered. 



Mr. N. H. Darton (U.S. Geol. Surv., Bull. 701, 

 1920) has brought together "all available published data 

 bearing on the rate of increase of underground tem- 

 perature with increasing depth in the United States," 

 including numerous original observations by the author 

 and his colleagues. Some of the very deep wells 

 drilled for oil give average rises of temperature of 

 1° F. for every 70 ft., the rise being near the surface, 

 and in the deepest levels being about 1° F. for every 

 60 ft. The following records are of special interest : — 

 McDonald, Pa. (6975 ft.), bottom temperature 

 144-9° F-; <^he Lake Well, West Virginia (7500 ft.), 

 at bottom i68-6° F. ; and the Goff Well in the same 

 State (7386 ft.), temperature at 7310 ft. 158-3° F. 

 The misleading nature of generalised calculations from 

 depths of less than a mile is clearly shown by the 

 fact that the Goff Well gives from 100 ft. to 7310 ft. 

 a rise of 1° F. for every 70-2 ft., and from 4000 ft. 

 to 7250 ft. of 1° F. for every 56-3 ft. The author 

 reminds us that the workings in the Comstock Lode, 

 Nevada, showed 170° F. at 3100 ft., the average in- 

 crease in the district being 1° F. for 33 ft. The rate 

 here decreases at similar horizons away from the 

 lode, and local volcanic material is inferred. 



The Bureau of Standards at Washington has issued 

 as Scientific Paper No. 406 a valuable review by 

 Dr. Coblentz of the present position of our knowledge 

 of the laws of radiation of a perfectly black body, and 

 the values of the constants which enter into the 

 numerical expression of those laws. He finds that a 

 considerable proportion of the discrepancies between 

 the results of determinations by different observers is 

 due to the neglect of the absorption of the radiation on 

 its passage from the furnace to the measuring instru- 

 ment, and to its partial reflection at the receiving 

 surface. On making suitable corrections for these 

 losses he finds that the results are brought into close 

 agreement. He gives as the best value of the coeffi- 

 cient of Stefan's law of total radiation 5-72 x lo"" ergs 

 per sq. cm. per second per fourth power of the absolute 

 temperature. For the constant C of Planck's radia- 

 tion formula he gives 14,320 micron degrees, and for 

 the product of the wave-length for maximum radiation 

 into the absolute temperature 2885 micron degrees. 

 The mean value of Planck's constant h by radiation 

 and other methods he gives as 6-55 x 10-" erg-seconds. 

 In the April number of the Journal of the Franklin 

 Institute, Messrs. Loyd A. Jones and C. E. Fawkes 

 give the results of their investigations into the action 

 of photographic reducers on the images produced on 

 NO. 2689, VOL. 107] 



development printing papers. The course of the 

 change is traced in each case by measuring the density 

 of the image after subjecting it to the reagent employed 

 for various times. It is possible to reduce so that 

 the contrast is either unchanged, diminished, or in- 

 creased. The chief point of novelty demonstrated is 

 the action of ammonium persulphate, which in the 

 presence of a little sodium chloride gives a nearly 

 proportional decrease of density. But if the per- 

 sulphate is dissolved alone in distilled water there is 

 a certain critical point on the density curve, on the 

 thinner side of which there is very little change, while 

 there is very vigorous action on the denser side. Even 

 in so short a time as three minutes, that part of the 

 curve that lies above the point is reversed in its curva- 

 ture, and parts of it become less dense than the critical 

 point itself. The authors give the formulae of the 

 solutions that they used. 



In his presidential address delivered recently to the 

 Institution of Mining and Metallurgy Mr. F. W. Har- 

 bord dealt with the chief metallurgical developments 

 which have taken place in this country since 1914. Ac- 

 cording to him, the only new industries which were 

 established as the result of war requirements were the 

 manufacture of tungsten powder and of ferro-alloys 

 generally. In regard to these products the country 

 is now able not merely to supply its own require- 

 ments, but also to compete in the chief markets of the 

 world. The output of carbon steel was increased by 

 more than 2,000,000 tons in 19 17 as compared with 

 19 13. More than one-half of this increase was due 

 to "basic" steel. In the years 1916-18 arrangements 

 were made for the erection of 22 blast furnaces and 

 166 open-hearth steel furnaces with a producing 

 capacity of more than 3,000,000 tons per annum. No 

 branch of metallurgy received a greater stimulus and 

 made greater progress than the art of making and 

 heat-treating special steels, especially those containing 

 nickel, chromium, and vanadium. For many years 

 before the war the zinc industry was in a languishing 

 condition. Here again the productive capacity of the 

 country has been much increased by the erection of 

 new plant and by extensions and improvements to 

 existing plants. The present position of this industry 

 is quite abnormal, but when the relation between 

 cost of production and market price becomes normal 

 Mr. Harbord is of opinion that this country will have 

 two very strong points in its favour, owing to the 

 Government control of Broken Hill ore supplies and 

 the better equipment of the extraction works. 



At the eleventh annual May lecture of the Institute 

 of Metals on May 4 Prof. T. Turner took as his sub- 

 ject "The Casting of Metals," which dates back to 

 early, antiquitv. The quality of the older material can. 

 not be equalled to-day, although output has been 

 enormously increased and the percentage of " wasters " 

 reduced. Aluminium presents special difficulty on 

 account of its high coefficient of expansion ; this leads 

 to fracture during cooling unless proper precautions 

 are taken. Gases In tion-ferrous metals are not so 

 important as In steel, and any metal or alloy which 

 does not develop gas by reaction or does not unduly 



