March 13, 1890] 



NATURE 



445 



the winds observed near land, the velocity at the different 

 hours of the day gives a curve as clearly and decidedly 

 marked as that of the temperature, the minimum occur- 

 ring from 2 to 4 a.m., and the maximum from noon to 

 4 p.m., the absolute maximum being at 2 p.m. The dif- 

 ference between the hour of least and that of greatest 

 velocity is for the Southern Ocean 6^ miles ; South 

 Pacific, 4i miles ; South Atlantic, 3J miles ; and North 

 and South Atlantic, each 3 miles. It is also to be noted 

 that even the maximum of the day near land in the case of 

 none of the oceans attains to the velocity observed over the 

 open sea. The curve near land is substantially the same 

 as the curves characteristic of stations on land. Thus, 

 over the sea, where surface temperature is practically a 

 constant day and night, the velocity of the wind shows 

 no diurnal variation ; whereas over land, and also near 

 it, where the temperature of the surface is subject to a 

 diurnal variation, the wind's velocity is also subject to an 

 equally well-marked diurnal variation. On the other 

 hand, at high-level observatories situated on true peaks, 

 the maximum velocity occurs during the night, and the 

 minimum during the day. In deep valleys in mountain- 

 ous regions, an abnormally high barometer obtains during 

 the night, which is the result of cold currents from the 

 adjoining slopes that the cooling effects of terrestrial 

 radiation set in motion. Now since these down-flowing 

 winds must be fed from higher levels than those of the 

 mountain itself, the winds prevailing on their tops are 

 really the winds of a higher level, and blow therefore 

 with the increased velocity due to that greater height. 

 On the other hand, during the warmer hours of the day, 

 the barometric pressure in deep valleys is abnormally 

 low, owing to the superheating of these valleys as con- 

 trasted with the temperature of the surrounding region, 

 thus giving rise to a warm wind blowing up the valleys, 

 and an ascending current close to the sides of the moun- 

 tain up to the summit. Now, since no inconsiderable 

 portion of this ascending current, whose horizontal velo- 

 city is necessarily much retarded, mingles with the air- 

 current proper to the level of the peak, the wind on the 

 peak is retarded, and falls to the minimum of the day 

 when the temperature is highest. 



The results of the averaging of the squalls over the 

 open sea entered in the Challenger'' s log show a strongly 

 marked diurnal maximum early in the morning, when 

 the effects of terrestrial radiation are at the maximum. 

 But over land the diurnal curves for whirlwinds, torna- 

 does, and allied phenomena, show the minimum at these 

 hours, and the maximum at the hours when insolation is 

 strongest. It is probable that the daily maximum occurs 

 in each case at those hours when temperature decreases 

 with height at a greatly more rapid rate than the normal. 



The distribution during the day of thunderstorms, and 

 of lightning without thunder, is very remarkable. During 

 the cruise 26 thunderstorms occurred over the open 

 sea, of which 22 occurred during the 10 hours from 

 10 p.m. to 8 a.m., and only 4 during the other 14 hours of 

 the day. Hence, over the open sea, the diurnal curve of 

 thunderstorms is precisely the reverse of what obtains on 

 land. Of the 209 reported cases of lightning without 

 thunder, 188 occurred during the 10 hours from 6 p.m. to 

 4 a.m., and only 21 during the other 14 hours of the day. 

 The following are the hours of the maxima of these 

 phenomena in the warmer months over land and the 

 open sea respectively. Thunderstorms over land, 2 to 

 6 p.m. ; lightning over land, 8 p.m. to midnight ; lightning 

 over the open sea, 8 p.m. to 4 a.m. ; and thunderstorms 

 over the open sea, 10 p.m. to 8 a.m. These facts are a 

 valuable contribution to the science, from their intimate 

 connection with the ascending and descending currents 

 of the atmosphere. 



The second part of the Report, dealing with the monthly 

 and annual phenomena, aims at giving a comparative 

 view of the climatologies of the globe to a degree of com- 



pleteness not previously attempted. The distribution of 

 the temperature and pressure of the atmosphere and 

 prevailing winds is illustrated by 52 newly constructed 

 maps, of which 26 show by isothermals the mean monthly 

 and annual temperature on hypsobathymetric maps, 

 first on Gall's projection, and second on north circum- 

 polar maps on equal surface projection ; and 26 show, 

 by isobars, for each month and for the year, the mean 

 pressure of the atmosphere, with the gravity correction to 

 lat. 45° applied, and by arrows the prevailing winds of the 

 globe. Two other maps are given in the text, one show- 

 ing for July the geographical distribution of the amount 

 of the barometric oscillation from the morning maximum 

 to the afternoon minimum ; and the other, the annual 

 range of the mean monthly pressure, which, in a sense, 

 may be regarded as indicating the relative stability of the 

 atmospheric pressure in different regions of the earth. 



For the details of this discussion, we must refer to the 

 Report itself, the broad results of which Mr. Buchan thus 

 summarizes : — 



" The isobaric maps show, in the clearest and most 

 conclusive manner, that the distribution of the pressure 

 of the earth's atmosphere is determined by the geo- 

 graphical distribution of land and water in their relations 

 to the varying heat of the sun through the months of the 

 year ; and since the relative pressure determines the 

 direction and force of the prevailing winds, and these in 

 their turn the temperature, moisture, rainfall, and in a 

 very great degree the surface currents of the ocean, it is 

 evident that there is here a principle applicable not 

 merely to the present state of the earth, but also to 

 different distributions of land and water in past times. 

 In truth, it is only by the aid of this principle that any 

 rational attempt, based on causes having a purely ter- 

 restrial origin, can be made in explanation of those 

 glacial and warm geological epochs through which the 

 climates of Great Britain and other countries have 

 passed. Hence the geologist must familiarize himself 

 with the nature of those climatic changes which neces- 

 sarily result from different distributions of land and 

 water, especially those changes which influence most 

 powerfully the life of the globe." 



It is evident from what has been said that many of the 

 results of the diurnal and seasonal phenomena of ocean 

 meteorology are equally novel and important, and, when 

 combined with the analogous results obtained from land 

 observations, enable us to take a more intelligent and 

 comprehensive grasp of atmospheric phenomena in their 

 relations to the terraqueous globe taken as a whole than 

 has hitherto been possible. 



THE BOTANICAL LABORATORY IN THE 

 ROYAL GARDENS, PERADENIYA, CEYLON. 



'"PHE attention of the readers of Nature has been 

 ■'■ drawn more than once (vol. xxxi. p. 460, vol. xxxiv. 

 p. 127) to the opportunities which are before botanists 

 for the study of plants other than those of our own flora. 

 But since the latter of these articles appeared, a step has 

 been taken which will justify a return once more to this 

 important subject. 



It is certainly one of the most healthy signs of the 

 present time that our younger botanists desire not merely 

 to pore over minute details of microscopical structure in 

 the laboratory at home, but to become personally ac- 

 quainted with plants in the open. When the somewhat 

 sudden reversion occurred some fifteen years ago, from 

 taxonomy as an academic study, to the more detailed 

 examination of the tissues of plants in the laboratory, and 

 the study of their functions, those who took a large view 

 of the progress of the science must have seen with regret 

 that the change, however valuable in itself, brought with 

 it a new danger. Those who as students were first 

 introduced to plants as subjects of microscopic study ran 



