AUGVST, 1904.] 



KNOWLEDGE c^^: SCIENTIFIC NEWS. 



169 



E. winds lower the temperature very nuich in winter, 

 and generally raise it in sunmier. 



S.E. winds do nearly the same, but less iiiarkrdly in 

 winter. 



S. winds raise the temperature much in wintei, hut 

 scarcely aflect it in summer. 



S.W. winds do nearly the same. 



W. winds decidedly raise the temperature in winter, 

 and lower it in summer. 



N.W. winds lower the temperature generally, but 

 mostly in summer. 



The most satisfactory way to ascertain the distribution 

 of temperature over a country is to prepare an isothermal 

 chart. This can be done by plotting on a map the tem- 

 peratures at a considerable number of stations, and 

 joining up the readings of the same values by lines which 

 are called " isothermals." From an examination of such 



the coasts ; the temperature thus not rising to the ex- 

 tremes which are experienced at inland stations. 



The temperature declines wilii increase of altitude at 

 the rate of nearly i ' in 300 feet ; so, in preparing isother- 

 mal charts, the temperatures must be corrected propor- 



Fig. 4.— Isothermals over the British Isles. Winter. 



maps, it is seen that the range of temperature is greater 

 over inland districts than near the coast. The sea has a 

 great equalizing effect on the temperature of the air 

 round the coasts, while inland the ground is warmed up 

 to a greater extent by the sun during the day, and is 

 chilled by radiation at night, and so has a more marked 

 efTect upon the air temperature. 



Isothermal charts of mean temperature for the British 

 Isles fo r the winter month of January and for the summer 

 month of July are given in Figs. 4 and 5. These are 

 based on 25 years' observations, 1871 — 1895, ^"<i "^^^ 

 from a paper by Messrs. R. H. Scott, and F. Gaster, in 

 the Quarterly Journal of the Royal Meteorological Society, 

 vol. xxiii., p. 275. 



The influence of the warm water of the Atlantic is 

 very clearly manifest in the January chart in the higher 

 temperatures on the western and south-western coasts 

 than over the central and eastern districts. In the 

 summer the sea has a moderating effect on the air round 



Fig. 5. Isothermals over the British Isles. Summer. 



tionately for the height of the station above sea-level. 

 The observations on Ben Nevis give a reduction of i" in 

 270 feet. Experimental observations in the free air are 

 now being made with self-recording instruments raised 

 by kites, in order to secure more complete data for deter- 

 mining the rate of decrease of temperature with altitude. 



In the valuable series of meteorological oljservations 

 which is issued each year from .Stonyliinst Obserxalory 

 a taljle is published from wiiich it ap|)ears that last 

 year's weather, un[)ii-asant and surprising as it was, 

 i)roke few old records at meteorological stations out- 

 side London. It was a year which, as Father .Sid- 

 greaves observes, will probaby be known for some time 

 to come as the " wet year," but it was not the wettest 

 known. For example, though its rainfall (at .Stony- 

 hurst) was 58.9 in., and ir in. above the average, it 

 was more than 3 in. below the 62.1 in. of the year 

 i8()'i ; and though rain fell on 21,1 days, this was not so 

 bad as the 319 days out of 365 on which rain fell in 

 1872. .'\ fact which emerges from Father .Sidgreave's 

 notes, though it is not coimected with last year's 

 weather, is that between the highest recorded reading 

 of the barometer in the last lifty-six years, which w;is 

 30.507 on January y, 189O, and the lowest, on Decem- 

 ber «, 1886, of 27.350 in., there is a difference of 3.247 

 ill. That we may take to be ec|ual to a difference in 

 pressure on the human frame of not less than a pound 

 • ind a half to the square inch — not less than a weight of 

 half .1 ton on the whole human body. 



