410 NATURE SEPTEMBER 9, 1933 from their burrows, were therefore carefully exam• from two to six hours. Buoyancy is evidently some• ined (July 31) and 20 of them found with slight to times lacking at the cloud base, but is developed heavy infection of an unidentified fungoid organism, higher up owing to the latent heat of condensation, exhibiting fungal-like threads extruding from the provided that the lapse-rate of temperature in the gills, or ramifying on the setre. It is not known surrounding air exceeds the saturated adiabatic rate. whether the presence of this organism on Arenicola At still greater heights the cloud top may penetrate is abnormal, but it seems probable that such an a more stable layer and again become colder than its infection may afford on further investigation a environment, but in the case of thunderstorms partial or complete explanation of the migration buoyancy is usually maintained to above 15,000 feet. from the burrows. The occurrence of a fungus in an The strong rising currents of thunderstorms are estuary noted for salmon is a matter of considerable evidently a late development, since otherwise the interest to those concerned in the health of this development of the storms would be much quicker important fish, especially as a pathogenic marine than it actually is. In the earlier stages there must fungus allied to the Saprolegniacere is known to often be a delicate balance between the factors pro• occur in Pinnothere.s3 • ducing ascent of air and those opposing it. Hori• Further investigations are highly desirable and zontal temperature gradients, convergence in the may reveal whether the recent unusual events• horizontal air motion (especially below 2,000 feet), in this district have a common cause and are related or topographical features on the ground play a part to alleged local pollution. The approach to sexual in most if not all thunderstorms, though these factors maturity shown in A. marina from half-tide level in are ineffective without a suitable lapse-rate of tem• this locality confirms the suspicion of Ashworth 4 perature higher up. that the 'littoral variety' on these coasts breeds The number of upper air soundings on thunderstorm towards the end of summer, whereas similar worms days is now very large, and it is found on these occa• living at the level of low-water springs in many other sions that by far the most potent forces of buoyancy localities usually breed in spring. acting on an air mass rising through its environment J. H. ORTON. act appreciably above the condensation level. In Department of Zoology, the absence of observations in the heart of the storms, University of Liverpool. it is usually assumed that the air rises adiabatically, Aug. 10. and though mixing between the rising air and its environment may modify this in practice, the general 1 Barcroft, J., and Barcroft, H., Proc. Roy. Soc., B, 96, 28; 1924. ' Orton, J. H., NATURE, 132, 314, Aug. . 26, 1933. qualitative conclusion regarding the main source of 'Atkins, D., J. Mar. Biol. Assoc., 16, 203; 1929. the buoyancy remains unaffected. Another com• • Ashworth, J. H., Cat. of Clu:et. in Brit. Mus., A., Polychreta Part 1, Arenicolidoo, 1912. plication is the cooling effect of precipitation, especially of hail and snow melting into rain. The air in a shower is normally colder than at the same Cumulus Clouds, Convection Currents and Gliding level outside it, often up to 5,000 feet, and probably IN his interesting letter on this subject!, Dr. sometimes higher. This destroys the buoyancy of the F. J. W. Whipple seems to imply that the coldness air, and the downward current causing the out• of a cumulus cloud relative to its environment rushing squall probably sometimes originates above represents a new discovery on the part of W. Kopp. 5,000 feet. The shower is maintained by fresh masses Perhaps I may be allowed to point out that I noted of rising air at its boundary, usually in front of it this fact in 1917 2 , and soon afterwards wrote in the but sometimes also (or altematively) behind or at columns of NATURE3 , " ••• the lapse-rate near the the sides. There is thus always a tendency for the ground is adiabatic, but this is not usually the case old parts of showers or thunderstorms to diminish, at the cloud level, with the result that the clouds and for the new parts to intensify. at the top of the ascending currents are usually C. K. M. DouGLAs. colder than the surrounding air". Later research 55 Elm Park Gardens, has shown that on a sunny day the lapse rate of London, S.W.IO. temperature considerably exceeds the rate Aug. 23. in a shallow layer near the ground. I mclme to the 1 NATURE, 132, 276, Aug. 19, 1933. opinion that the rising air mass resembles a bubble, 1 J. Scot. Meteor. Soe., 17, 140; 1917. and that it gains vertical velocity in the lower 3 NATURE, 101, 87, April 4, 1918. unstable layer, and loses it higher up, but is carried by its own past its equilibri?I? position. If this view IS sound, It follows that a nsmg current The Knock-Rating of Heptine-1 should be found only under a developing cumulus IN the past few years a large number of pure cloud, but that under a dissolving cloud the motion hydrocarbons have been tested as regards their should be downward. It would be interesting to knock-rating in test engines and it is now possible know whether gliders can confirm this. to compare many pure hydrocarbons that boil in As regards large cumulus and cumulo-nimbus the petrol range as regards their engine performance. clouds, I find among my War-time notes a number Collected data on the knock-ratings of pure par• of observations on this subject. The temperature affinic, naphthenic, unsaturated naphthenic, aromatic in the cloud was sometimes lower than in the adjacent and olefinic hydrocarbons have recently been air at the same level, sometimes higher, and some• published by one of us (F. H. G.) and Evans, Sprake times about the same. On showery or thundery and Broom1 • It was thus desirable to extend this days the cumulus clouds are started off in much the list to include a liquid acetylenio hydrocarbon. same way as on fair days. If one watches the clouds Heptine-1 was prepared by the method of Meunier 2 3 carefully, one sees that some of the and Desparmet and Bourguel by the action of away, while others continue to grow and JOin with sodamide on 1 : 1 : dichloroheptane, the latter being others usually along a belt, and perhaps finally prepared by the action of phosphorus pentachloride form thunderstorms, after a total period varying on heptaldehyde'. In the sodamide-dichloroheptane © 1933 Nature Publishing Group