March 8, 1917] 



NATURE 



27 



ing group, which gives a large value of K, could 

 be attributed to greater mass, and not merely to 

 greater volume, it might be possible to regard 

 K as a function of the mass. The effect of great 

 mass might then be to produce the pressure dis- 

 placement mentioned by Campbell as a possible 

 •explanation. Or, as Dr. Herassimovitch points 

 out, a displacement of the stellar lines to the red, 

 such as would account for the K term, might 

 possibly result from the gravitational field in the 

 •case of great masses, in accordance with Freund- 

 lich's deduction from the theory of relativity. 

 There appear to be some difficulties, however, in 

 ■connection with the latter hypothesis, and it may 

 be added that the Mount Wilson observers have 

 been unable to detect any systematic effect of 

 this kind in the case of the sun, although the 

 •calculated effect is considerably greater than the 

 errors of observation (Mt. Wilson Report, 1914, 

 p. 255). On either supposition, however, it 

 seems improbable that there would be so great a 

 •difference in masses for Lockyer's two groups of 

 helium stars as to account for the large value of 

 K in the ascending group and its practical dis- 

 appearance in the descending group. 



It at least seems clear, from the above results, 

 that K can no longer be regarded as a constant 

 ■error, having a fairly definite value for each of 

 the Harvard classes. Prof. Perrine has also 

 recently been led to this conclusion (Astrophys. 

 Journ., November, 1916), and is inclined to the 

 opinion that the observed residuals represent 

 velocity displacements. Whatever the true ex- 

 planation maybe, Dr. Herassimovitch 's investiga- 

 tion emphasises the importance of taking account 

 of Lockyer's criteria in the classification of stars 

 )f the helium group. A. Fowler. 



THE POTATO SUPPLY. 



'T'HE average potato crop of Great Britain is a 

 -»- little over 2 million tons, and that of Ireland 

 a little under this figure. Great Britain and 

 Ireland together contribute rather less than 5 

 per cent, of the world's crop of 91^ million tons. 

 In normal years the British Isles grow nearly, or 

 quite, enough potatoes to satisfy home needs. 

 Accessory supplies are, however, derived from 

 the Channel Islands, Normandy, Brittany, and 

 other sources. 



Hence it might be doubted whether even in 

 these exceptional times there is need for any large 

 measure of forethought or room for much anxiety 

 with respect to our f)otato supplies. 



A combination of circumstances, however, has 

 co-operated to make this year's potato crop a 

 matter of considerable national importance. 



First among these circumstances is the fact that 

 very large quantities of potatoes are required for 

 his Majesty's forces. Moreover, there is reason 

 to believe that the French have been large pur- 

 chasers. Secondly, last year's potato crop was 

 below the average, both in Scotland and in certain 

 parts of England. In some districts the crop, 

 though fair in amount, proved to be badly 



NO. 2471, VOL. 99] 



diseased at lifting time ; a sure indication of loss 

 in store. Exact information as to the total yield 

 in this country is not available, but it may be 

 taken as probable that it does not amount to two- 

 thirds of the average crop. 



The reasons for the shortage are numerous, but 

 one of the chief is undoubtedly the adverse season 

 of 1916; lack of labour for hoeing, absence of 

 supplies of potash manures, and the high price 

 of other artificial manures also contributed to the 

 misfortune. 



In consequence of the partial failure of the 

 crop it was foreseen that prices would rise to a 

 high level, and it was hof>ed that official action 

 would be taken while the bulk of the crop was in 

 the ground, and before contracts were entered 

 into. The hope was not realised. Warnings 

 were ignored — for to warn before it is too late 

 is to be premature. More serious than the rise in 

 price of ware (food potatoes) was the rise in 

 the price of seed. Scotch seed, which, together 

 with Irish, gives a higher yield than English 

 seed, was known to be scarce, and thrifty men, 

 in order to secure seed betimes, paid so much as 

 25Z. to 30/. per ton for seed of good varieties. 



At this stage prices were fixed — maximum 

 price for last year's crop, maximum for the crop 

 not yet sown, and for the seed for sowing. The 

 price fixed for next year's crop had the immediate 

 effect of determining everyone whose patriotism 

 was not very much deeper than his pocket to 

 abandon the idea of growing potatoes, for they 

 knew that a maximum price of 1 155. -1305. per ton 

 would mean growing the crop at a loss. Plain 

 men were puzzled to know why a beleaguered city 

 must at all costs save itself from a glut of 

 pKDtatoes. There was an outcry, and the maxi- 

 mum price for next year's crop became a 

 minimum. 



\\' ith respect to seed the fixed prices remain : 

 12/. per ton as a maximum, and at the present 

 moment anyone who wants to grow potatoes can, 

 as we are assured by the Board of Agriculture, 

 buy the hesi seed from the Board at 12Z., or from 

 any of the leading seedsmen at double the price. 

 If the article supplied by the Board proves indeed 

 to be the best with respect to origin, size, and 

 trueness to name, purchasers who waited on 

 providence will have reason to laugh at their more 

 provident brother-growers who bought betimes. 

 The authorities have gone one better than the par- 

 able : the late-come labourers get twop>ence instead 

 of the penny earned by those who bore the heat 

 and burden of the day. Nevertheless no public- 

 spirited person will grumble if he can be assured 

 that the Board has dealt justly with the grower 

 of the seed, and is able to supply seed tubers of 

 the best quality at 12/. per ton. Rather will he 

 incline to a belief in miracles. The view is 

 commonly held that there will be too many 

 potatoes grown this year. Facts, however, do 

 not warrant that view. There is a general short- 

 age of corn crops, transport is disorganised, 

 farm lands lack expert labour, artificial manures 

 are dear and scarce, and seed is likely to be of 



