552 



NATURE 



[June 30, 192 1 



matter to write about — rarely anything novel — or can 

 produce doctrine worth consideration. Usually they 

 are but dealers in hashed mutton ; they may spice 

 it pleasantly but it is still hash. " It is astonishing 

 what nonsense able men will sometimes write, just 

 because they don't know even the elementary laws 

 of scientific investigation," said Warde Fowler. 



I have a letter of his before me, from Kingham, 

 Chipping Norton, dated July, 1913, acknowledging a 

 pamphlet on Nature Study which I had sent to him : — 



I must confess (he writes) to an innate aversion 

 from " Nature Study " in inverted commas and 

 capital letters, i.e. as practised in too many schools, 

 because I know that the teachers are quite ready 

 to "teach " what they don't understand a bit and 

 that the only person who can really help the 

 children in these things is one who is learning 

 himself all the time and learning not only from 

 books but using them just as a help. I am very 

 glad to see that you have the same kind of feeling. 



Then he speaks of his work in the village school : — 



This week, for example, I have given away two 

 copies of my recent book on this village (which is 

 sought after in the village) as prizes for accounts 

 of the growth of corn (which is growing all around 

 us in different stages) from the seed to the fruit, 

 with specimens. Two girls won the prizes and 

 * there were some dozen good answers. The boys 

 seemed more interested in the processes of agricul- 

 ture than in the growth of the plant and the boys 

 are fewer in number than the girls. I myself have 

 learnt much that I did not know before and so 

 has the schoolmaster. They were all silent or in 

 difficulties about the bloom of the corn and no 

 wonder. What a number of beautiful and interest- 

 ing things there are to be learnt about it. To-day 

 I have been learning something about the corn 

 smut and turned out a book about diseases of 

 cereals which I had hardlv opened since I wrote 

 my " Roman Festivals " and wanted to know 

 something about the robigo, for the Festival of 

 Mildew (Robigalia). One wants a microscope, how- 

 ever, to interest children in such things as that. 



I feel as if I should like to go on talking to you 

 but I must be content with thanking you for your 

 reminiscence of my young friend Jim Holmes, for 

 whom I still have a sneaking fondness, as the 

 only (or almost the only) creature of my brain. 



In the "Roman Festivals," a work of marvellous 

 erudition and research, he devotes quite a long section 

 to the discussion of the Robigalia and remarks that 

 " the red mildew was at times so terrible a scourge 

 that the Robigalia (April 25) must in early Rome, 

 when the population lived on corn grown near the 

 city, have been a festival of very real meaning. A 

 red dog was sacrificed to Robigus, the spirit who 

 works in mildew. Nowadays nothing that happens 

 in ag'ri culture is marked by sacrifice." 



Whether we think of Warde Fowler as literary 

 man or naturalist, however, for the man who could 

 write : — 



I will tell you that the joy of discovering some- 

 thing that you did not know before is in my ex- 

 perience very great and that the joy of finding 

 that so far as your knowledge goes no one ever 

 found it out before is far greater, 



we shall long keep a place in our memory. Oxford 

 will best serve his memory by increasing the number 

 who can have that joy, as to-day, it may be feared, 

 we are farther off than we ever were from that 

 " general and vehement spirit of search in the air," 



NO. 2696, VOL. 107] 



which Lord Morley long ago proclaimed to be our 

 prime need : not a few schools, too, are aiming at a 

 classical revival ; the meaning of science is not yet 

 with them generally. 



H. E. A. 



lonisation Potential and the Size of the Atom. 



It is known that there is for different elements a 

 relation between the ionising potential and atomic 

 volume, the one increasing- as the other diminishes. 

 Hughes in his book on "Photo-electricity" (p. 51) 

 indicates that the work in removing an electron wholly 

 from an atom might be expected to vary inversely as 

 the radius. In other words, the ionising potential 

 might be inversely proportional to the cube-root of 

 the atomic volume. 



Now W. L. Bragg-, in the Philosophical Magazine 

 (August, 1920), has given the diameters of atoms in 

 .^ng-strom units (10- 'cm.), on the assumption of close 

 packing in crystal structure. The diameter which he 

 determines is more strictly the distance from centre 

 to centre of contiguous atoms of the same kind. The 

 dimensions which he thus found are far smaller than 

 those deduced from calculations by kinetic theory. 



It appears desirable to make a comparison of the 

 ionisation potentials (i) with the diameters as given 

 by W. L. Bragg, and (2) with the cube-root of the 

 atomic volume. 



In the subjoined table the name of the element, 

 the ionisation potential, and Bragg's diameter ( x 10'), 

 are set forth in the first three col'imns. The product 

 of the diameter and ionising- potential appear in the 

 fourth column. The cube-root of the atomic volume 

 is stated in the fifth column, and its product with 

 the ionisation potential in the sixth column. 



Group I. 



