;94 



NATURE 



[July 12, 1917 



The Temperaxcrk of Space. — In a communication 

 to the Astrophysical Journal, vol. xlv., p. 269, Prof. 

 Fabry arrives at the interesting- conclusion that while 

 the idea of temperature at a point in free space has 

 no meaning in itself, the temperature of a testing 

 body maj" vary enormously according to its absorp- 

 tive properties. A testing body having a black sur- 

 face is of no special theoretical interest, but a body 

 with selective absorption may attain a temperature 

 much lower or much higher than that of a black 

 body, according to the wave-length of its absorption 

 band. If the body be very absorbent for long wave- 

 lengths, and only slightly so for short wave-lengths, 

 it will radiate like a black body, but will absorb 

 scarcely anything, and its temperature of equilibrium 

 will be very low. On the other hand, if the body 

 strongly absorbs the short wave-lengths, and has zero 

 absorptive power (and consequently zero emissive 

 power) for long wave-lengths, its temperature will 

 continue to rise until it becomes capable of emitting 

 the corresponding short wave-lengths. At the earth's 

 distance from the sun, a body with a single absorp- 

 tion band at 04 ju would reach a temperature of about 

 1980° — nearly the melting point of platinum — ^by 

 simple exposure to the rays of the sun ; while a black 

 bodv under the same conditions would only reach 

 280°. Prof. Fabry considers it not impossible that 

 some action of this kind may be effective in main- 

 taining gaseous masses in space at a high tempyera- 

 ture, and he suggests that the luminosity of the tails 

 of comets may be a purely thermal radiation due to 

 the very high temperature produced by a slight selec- 

 tive absorption exerted upon the solar rays. 



Radial Velocities of Five Cepheid Variables. — 

 Investigations of the radial velocities of the southern 

 Cepheid variables, S Muscas, R Tri. Aust., S Tri. 

 Aust., S Normae, and RV Scorpii, have been made 

 by G. F. Paddock (Lick Obs. Bulletin, No. 294). 

 Variations in the apparent radial velocity were found 

 in each case, the amplitudes being 33, 33, 28, 24, and 

 32 km. respectively. It is concluded that these 

 Cepheid variables possess the distinguishing charac- 

 teristics found in others of their class, namely, con- 

 siderable eccentricity ; similar order of amplitude of 

 velocity, 20 to 40 km. for the majority; greatest 

 negative velocity occurring a few tenths of a day 

 later than maximum light ; and close correspondence 

 between times of maximum velocitv and minimum 

 light. 



THE AUSTRALIAN WATER PROBLEM.^ 



'T^HE great island-continent of Australia admittedly 

 -*- possesses a wonderful store of natural wealth 

 which only needs exploitation to render the country 

 one of the richest and most productive of British 

 territories ; and yet development proceeds but slowly. 

 The agricultural and pastoral mdustries, for example, 

 have bareW taken root ; out of a possible 200,000,000 

 acres only 12,500,000 are producing wheat at the 

 present time. The population, too, is the scantiest of 

 any of the civilised countries of the world, being only 

 17 to the square mile. The reason for this back- 

 wardness perhaps is not far to seek. Notwithstanding 

 its remarkable endowments, the country is beset by 

 a very serious disability. Vast tracts of it are desert 

 waste, and, with the exception of the coast-line, the 

 whole is more or less afflicted by visitations of 

 drought. 



So vital a defect calls for energetic measures, and 



1 " Water Supply in the Interior of Western Australia." By P. V 

 O'Brien. " "ITie Coolgardie Water Supply, Western Australia." By_ P. V. 

 O'Brien and f. Parr. Papers read before the Institution of Civil Engineers, 

 London, on April 3. 



NO. 2489, VOL. 99] 



much has already been done to promote artificial 

 irrigation wherever practicable. Fortunately, the arid 

 tracts are not without compensating features. Various 

 basins have been traced where water can be obtained 

 by sinking artesian wells. In the year 1915, accord- 

 ing to the report of the Royal Dominions Comhiission, 

 then,' were no fewer than 3470 of such borings, rang- 

 ing in depth down to 5000 ft. From some ot them 

 the outflow was remarkable. One case is cited of 

 a daily flow of no less than 4,500,000 gallons. 



The two papers before us deal with the practical 

 steps taken to obtain supplies in Western Australia, 

 and, more particularly, in that portion of it which 

 centres in the mining district of Coolgardie and Kal- 

 goorlie. "Speaking generally," says Mr. O'Brien, 

 "the country north of 29° S. lat. contains fresh water 

 at fairly shallow depths, while south of that latitude 

 the water is salt." Towns and industries to the north 

 of the line are supplied with water from groups of 

 wells spaced lo to 20 chains apart, round a central 

 pumping-station. In the southern section water fit 

 for human consumption can be obtained only by con- 

 servation of the rainfall before infiltration. The 

 underground water contains sodium chloride and 

 other salts, in proportions from 5 oz. to 12 oz. to the 

 gallon, and is, accordingly, suitable only for ore- 

 washing and similar purposes. 



The fresh-water wells range in depth from 50 ft. to 

 120 ft., and cost from 3Z. to ^l. los. per foot of depth. 

 .A. considerable number have been constructed by the 

 Water Supply Department, at intervals of ten to fifteen 

 miles along the roads which have been cleared for 

 several thousand miles through the mining district. 

 The surface of the country is undulating, ranging in 

 altitude from 1200 ft. to 1500 ft. Its formation is 

 mostly red sandy loam and granitic sand, overlying 

 laterite and conglomerate. 



Conservation of rain-water is effected with the aid 

 of storage- tanks, and when these are appropriately 

 situated in the scattered outcrops of solid granite 

 (some of 300 acres in extent) as much as 95 per cent, 

 of the first inch of rain has been conserved, and from 

 rains quickly following, 100 per cent. In other catch- 

 ment areas, when the surface , is clay loam, con- 

 glomerate, etc., the natural water-courses are utilised 

 so far as possible for collection, the beds being recti- 

 fied wherever necessary to eliminate scour. In order 

 that the water may quickly reach the leading drains, 

 a network of plough furrows is often driven in the 

 adjacent land. 



Tanks vary in capacity from 1,000,000 to 3,000,000 

 gallons. They may be simple excavations, or pits, in 

 watertight ground; in other cases they are formed 

 with clay puddle embankments and beds, or are lined 

 with concrete or asphalt. The concrete tanks did 

 not prove a success, as when no rain fell for a con- 

 siderable period serious cracking developed in the 

 concrete, in spite of a roofing of corrugated iron. 

 The asphalt tanks, constructed under conditions de- 

 scribed in the paper, have satisfactorily fulfilled all 

 requirements. There are a few instances of iron 

 tanks of 10,000 to 20,000 gallons capacity. 



The towns of Coolgardie and Kalgoorlie differ from 

 other populous centres in that their water-supply is 

 obtained from a joint source in the Darling Range, 

 at a mean distance of 340 miles. The Helena reser- 

 voir is fed from a catchment area of 569 square miles, 

 and the water so obtained is pumped through a pipe- 

 line of 30-in. diameter steel piping to its destination. 

 The catchment area lies in hilly country, rarely, how- 

 ever, exceeding an elevation of iioo ft., and much 

 intersected by narrow and steep-sided valleys. The 

 surface is heavily timbered and cumbered with under- 

 growth. The soil is an ironstone grravel overlying 



