47" 



NATURE 



Febri M-, [^ i()H) 



loped fi ■ mi supercooled iti r-drops 

 cumuli i-nimbus i loud. s 

 minute ice-crystals, which sparkle in the sun and 

 causi halo phenomena, are found Floating about the 

 ol showei s, 



o ft. I louds i onsisting of supei li d drops 



cause corona rings, and sometimes also fog-bows. 

 Fig. 3 shows large towering cumuli ovei the land 



ho Hi. i , vening, with their lias, s at 51 



.mil their tops fully 15,000 ft. The) were caused !>\ 

 un powerful upward currents developed in the lowei 

 atmosphere, where the lapse-rate reached the adia 



foi dr) air. The lapse-rati above 1 ft. was clo 1 



enough to the adiabatic foi aturated air to allow the 

 1 louds to towei upwards. I he) Rnallj broke up with- 

 out developing into thunderstorms. Fig. 4 shows 

 the rounded top of a cloud extending from 2500 ft. 

 to 10,000 ft., which caused a shower. A powerful 

 upward current in the lower air caused the top to 

 rise until it was colder than the air surrounding it, 

 as frequentl) happens, but h soon sank down again. 

 The temperature was 54 F. at 2000 ft., \<a 

 (1000 ft., and 30° at 10,000 Ft. I he photograph also 

 shows a snow shower falling for 2000 ft. or 3000 ft. 

 from a thin high cloud, and then evaporating, and 

 cirro-stratus clouds at a great height. 



Mam cloud-sheets develop in layers of high relative 

 humidity as the result of gradual vertical movements 

 over a wide area, which may affect stable layers 

 thousands of feet in depth. These vertical movements 

 are associated with the complex wind system which 

 often exists in the lower atmosphere, due to a complex 

 i.tl structure. They remain gradual so long as 

 conditions are stable, but may have important con- 

 sequences with certain distributions of upper-air tem- 

 perature and humidity. Sometimes clouds develop at 

 about 6000 ft. or Sooo ft., when the temperature is 

 unusually high at their level and the lapse-rate above 

 them is unstable, so that they ultimately grow to 

 thunderclouds with their tops above 20,000 ft. This 

 process must not be confused with that illustrated b) 

 Figs. 1 and 2, when the clouds grow up through a 

 cloud-sheel from a low level. 



In the front half of depressions the humidity is 



sometimes high from a low level up to al 



15,000 ft., with either a series of cloud-sheets near 

 together or a thin, ill-defined mist of great depth. 

 Steady rain readil) develops from such clouds, but 

 this is unlikely to be heavy unless the conditions are 

 unstable. Favourable conditions for heavy rain occur 

 when there is a cold body of surface air to displace 

 the warm, damp current, and also an unstable lapse- 

 rate of temperature in the upper air, so that the 

 warm air rises bodily and pails with it- moisture. 

 The lapse-rate is not necessarily high near the sur- 

 face; it is clear that with a given surface tempera- 

 ture the possible water-content of the atmosphere is 

 much greatei when the temperature is high to about 



61 ft. than when it falls off rapidly from the surface 



upw aids. 



An interesting problem on which aeroplane observa- 

 tions throw some light is that of visibility. The 

 present writi i as made observations in different places 

 which show thai much of the smoke from towns and 

 factories travels for hundreds of miles. In winter it 

 usually lies near the ground, but in summer the 

 convection currents carry it up to 6000 ft., and some- 

 times to 10,000 ft. If there is an inversion above the 

 haze, the top is sharph defined. A little smoke-haze 

 is sometimes met with at great heights, but it is 

 nearly always possible to see the clouds to the 

 horizon. 



Regular observations ol I lerature and humidit) 



in the upper air at several stations would be of great 



XO. 2572, VOL. I02] 



11 I 



the minor it 1 



on thi w< athi r, and should en- 

 id forecasts to he made with 



confidence than has hill,- 



accumulation m data as in the 



in the various currents whi< h r< ach oui ho 



lead to results ol fai 



logy. (''. K. m. i),,, ,., 1S . 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



I. DM" in. A nun se hi threi lei tures mi " I In Prin- 

 ciples hi Palaeobotany " will bi given at University 

 College l>\ I >i . Marie Stopes mi I hursdays, Fi b 

 ami March and ij, at 5 p.m. The lectures will be 

 spei tall) adapted to studi nts ol botan) ami 

 Inn an open in membi rs 1 ral public who 



in. i\ in interested in them. 



Oxford. Congregation has latelj approved the 

 preamble of a statute putting the professorship of 

 forestr) held by Sir William Schlich on a permanent 



basis. Ever since the transfer, some fourteen years 

 ago, 11I the Coopers Hill School to Oxford, the study 

 ot forestr) has continued m assume increasing import- 

 aim among the studies "i the University. This has 

 been in chief measure due to the zealous activity of Sir 

 William Schlich himself, .md in the wise co-operation 

 nl several ol the colleges, notably Magdalen and St. 

 John's. Tin recent establishment of .1 new school of 

 agriculture and forestry, supplementary to the former 

 diplomas in those subjects, is an experiment which 

 will I,, watched with interest, especially as it met with 

 some criticism in its earl) stages. But there is much 

 reason in believe that the stud) ol these subji cts will 

 attain a -iill higher degree oi efficienc) than at 

 pi esent . 



Congregation will shortly have before ii a statute 

 for the reform of Responsions. This measuri 

 carried in its present form, will have tin effect of 

 making either Latin or Greek optional in the examina- 

 tion, and either mathematics or natural science 

 obligatory. 



St. Andrews. — The University ('nun has announced 



that, under the will of the late Mrs. Purdie, widow 

 of Emeritus Prof. Purdie, the residue of her estate, 

 amounting to about 25,000/., has been bequeathed to 

 the University. This bequest is to he applied exclu- 

 sively to the promotion of research in chemistrj at 

 St. Andrews, and, together with the existing endow- 

 ment of the chemical research laboratories, place! 

 the disposal of the Universit) a total of approximately 



;;. /. for the prosecution of original work in this 



subject. The gift, the terms of which permit of the 

 income being used for the purchase < » f research equip- 

 ment and for the foundation of research scholarships, 

 is a fitting close to a long list of benefactions which 

 the chemistry school of St. Andrews owes to tin Purdii 

 family. 



The development of the chemistry department of 

 the United College as a centre for research is 

 largely due to the efforts of the late Prof. Purdie, and 

 when, in tSiin, the accommodation of the laboratories 

 I. .cami insufficient, a new laboratory for under- 

 graduates was presented in the University by his 

 aunt, Mrs. Purdie, of Castlediff. Ten years later 

 Prof. Purdie built and equipped at a cost of about 

 i5,oool. a separate instituti for chemical research, and 

 as both the University and the Carnegie Trust joined 

 in the scheme, it was possible to create a special 



