37^ 



NATURE 



[May 20, 1920 



its poles an flectromotive force of the order of 10" 

 volts. It tends to maintain an electric current from 

 the earth to the conducting layers of the upper atmo- 

 sphere or in the reverse direction, according as its 

 polarity is + or — . The difference which must exist 

 i« the conductivity of the air above showerclouds of 

 -f and of — polarity respectively, owing to the large 

 difference betwe<Mi the mobilities of the negative and 

 positive ions dragged out of the conducting layer bv 

 the field of the cloud, furnishes a possible explanation 

 of the normal positive potential gradient at a distance" 

 from showerclouds. It is also shown that it will 

 account for the prevailing negative sign of the poten- 

 tial gradients associated with showerclouds and for 

 the preponderance of positively chaj-ged rain and posi- 

 tive lightning discharges, i.e. discharges which pro- 

 duce a positive change of potential gradient. — L. F. 

 Richardson : The supply of energy to atmospheric 

 eddies. Osborne Revnolds investigated the energv of 

 eddies as a balance between income and expenditure. 

 The income was the activity of the eddy stresses 

 upon the corresponding rates of mean strain ; the 

 expenditure was by way of molecular viscosity. His 

 theory refers to an incompressible liquid, but it is 

 shown in the present paper that the same applies to 

 an elastic fluid. In a gravitating atmosphere there 

 is an additional channel for gain or loss, because the 

 eddies act as thermo-dynamic engines, either produc- 

 ing or decreasing inequalities of temperature. Thev 

 are, however, imperfect engines. It is shown that 

 the activity contributed by the eddies bv this pro- 

 cess is 



. '-' ^, PSf volume, 



where g is the acceleration of gravity, yp the thermal 

 capacity per mass, c the eddy-conductivitv, o- the 

 entropy per mass, and h the height. In the actual 

 atmosphere this activity is ordinarily an exoenditure 

 bv the eddies. Bv balancing it against their income a 

 criterion of turbulence is obtained. Some observations 

 of the quiescence of wind on a clear evening tend to 

 confirm the theory. 



Geological Society, May 5.— Mr. G. W. Lamplugh, 

 vice-president, in the chair,— S. H. Warren: A 

 natural " eolith " factory beneath the Thanet Sand. 

 The paper describes "a section in the Bullhead. 

 Bed at Grays, where the conditions have been favour- 

 able for the chipping of the flints by subsoil pressure. 

 There is evidence of extensive solution of the chalk 

 beneath the Tertiary deposits, and the differential 

 movements thus brought about have occasioned much 

 slickensiding, and remarkable effects in the chipping 

 of the flints. In the author's opinion the section 

 affords the most complete and conclusive evidence 

 hitherto obtained in support of the theory of the origin 

 of the supposed eolithic implements by purely natural 

 agencies. There are not onlv the simpler Kentish 

 types, such as notches, bowscrapers, and the like, but 

 also the larger and more advanced forms of rostro- 

 carinates, which are characteristic of the sub-Crag 

 detritus-bed. Careful digging enables the pressure- 

 points of one stone against another and the resultant 

 chipping effects to be studied in detail ; and in many 

 instances the flakes removed can be recovered and re- 

 placed. A few examples are more than merelv eolithic 

 in character. If such exceptional examnles were re- 

 moved from their associates, and also from the evi- 

 dences of the geolo£?icnl forces to which thev have 

 been exposed, no investigator could be blamed for ac- 

 cepting them without question as of Mousterian work- 

 manship. Individual specimens mav often deceive : in 

 order to distin£*uish a, geoloj^ical deposit of chipped 



NO. 2638, VOL. 105] 



flints from the debris of a prehistoric chipping-floor, it 

 is necessary to base one's judgment upon fairly repre- 

 sentative groups, and also to take into consideration 

 the circumstances in which they have been discovered. 



Cambridge. 

 Philosophical Society, March 8.— Mr. C. T. R. 

 Wilson, president, in the chair.- — H. H. Brindley : 

 Further notes on the food-plants of the common 

 earwig (Forficula aurictdaria). The observations on 

 the food-plants of the common earwig made on a 

 small scale in 1917 (Proceedings, xix., part 4, 191S, 

 p. 171) were continued in the summers of 1918 and 

 1919 on earwigs kept in captivity in connection with 

 a statistical inquiry on variation. Altogether about 

 ninety species of common plants, chiefly garden 

 varieties, were used. Among the most favourite foods 

 were the leaves of Jerusalem artichoke, beetroot, pink 

 begonia, garden cabbage, centaurea, delphinium, 

 leek, Malvus sylvestris, vegetable marrow, mignonette, 

 white pyrethrum, scarlet runner, seakale, and tomato ; 

 and the petals of blue Anchusa, China aster, pink 

 begonia, blackberry, different varieties of campanula, 

 white clematis, dandelion, Gesneria, white marguerite, 

 mint, corn parsley, white phlox, yellow CEnothera, 

 rose, tomato, red valerian, blue verbena, and varieties 

 of vetches. Among fruits green fig, honeysuckle, and 

 plum were well attacked, while apple was neglected 

 until the skin was removed, and then eaten com- 

 paratively little. Potato and artichoke tubers, save 

 dormant buds on the latter, escaped attack in their 

 skins, but when sliced they were thoroughly devoured. 

 The hairy undersides of the leaves of raspberry and 

 blue verbena and the curled edges of .Scotch kale 

 leaves are very • attractive to earwigs for hiding in in 

 the dav-time, and onion inflorescences, poppy cap- 

 sules, buds of hollyhock, petals of garden chrysanthe- 

 mums and snapdragon are also popular refuges. The 

 last two and Scotch kale leaves were also nibbled 

 moderatelv, but the conclusion formed in 1917 that 

 the actual damage done to chrysanthemums by ear- 

 wigs is usuallv exaf?i?erated was confirmed by the 

 later observations.— Miss Maud D. Haviland : Pre- 

 liminary note on antennal variation in an Aphid 

 (Mvzus' ribis, Linfi.). The red currant Aphis (Myzus 

 ribis, Linn.) shows variation of the antennae in the 

 winged females, according to whether they are fed 

 upon healthy leaves or upon leaves blistered bv the 

 sucking of previous generations. In forms from the 

 blisters the large sense-organs, situated upon an- 

 tennal joints v. and vi., are placed nearer the articula- 

 tion of these joints than in forms from healthy leaves. 

 Experiments on transference of blister-fed descendants 

 of a single ancestor to healthy leaves showed but 

 slight change in the first two or three generations. 

 Subsequent generations, however, showed marked 

 increase above the ancestral mean, though identical 

 generations, fed onlv upon blistered leaves, had a 

 mean similar to that of their ancestors. — Dr. Fenton 

 and A. J- Berry : Studies on ('ellulose acetate. The 

 authors ?ave a short account of certain observations 

 of general chemical interest obtained in the course 

 ("if an invpstigation on aeroplane dopes. — G. T. 

 Bennett : The rotation of a non-spinning gvrostat, 

 and its effect in the aeroplane compass. "A sym- 

 metrical wheel free to rotate about its axle is moved 

 from rpst in anv position bv means of the axle, and 

 is finallv restored to a position in which the axle 

 asrain points in the same direction as formerlv. Show 

 that the wheel, af*ain at rest, will have rotated 

 through a plane anf»le equal to the solid an£»le of the 

 cone described bv the varvinfj directions of the axle" 

 CColleee Examination Problem Paper, 1898). The 

 kinematics of the angular motion of the wheel is 



