84 



XXIII. 



OTJE CLIMATE. 

 Abstract of a Popular Lecture 



GIVEN BY 



Mr. G. DOWKER, F.G.S., 

 At Dovek, February 2nd, 1892. 



In this Lecture Mr. Dowker drew attention to the fact, that the 

 climate of the British Isles was governed by a great variety of physical 

 and astronomical causes, and had accordingly altta'ed from time to time. 

 It was pointed out that to understand the problem, it was necessary to 

 study all these factors. 



The Lecturer briefly explained the astronomical aspect. The cause 

 of the seasons, the position of the earth in perihelion and aphelion, the 

 equinoxes, the direction of the earth's axis, and the changes that would 

 be produced by any change in its direction ; and it was noted that 

 astronomers had calculated from the rate of precession of the equinoxes, 

 and the nutations in the orbit of the earth's eccentricity, that a period 

 of 21,000 years would be required for the seasons to make a complete 

 revolution, and in half that time the earth's position at the summer and 

 winter solstice would be exactly opposite to the present ; so then the 

 winter solstice would occur when we were furthest from the sun, and 

 the summer solstice when we were nearest. 



Physicologists were not agreed what the effect of these changes in 

 the astronomical position of the earth in these opposite conditions would 

 be; some, as Dr. "W. W. CroU* and Sir Charles Lyell had endeavoured to 

 minimise the effects, while lately. Sir R. Ball, in a treatise on " weather 

 on glacial conditions," had arrived at an opposite conclusion. 



Mr. Dowker then mentioned the disturbing causes that wouldinflueuce 

 the climate of any specified locality, summarising them as : — 1 st, 

 Proximity of land to the sea ; 2nd, Height of the land above the sea 

 level ; 3rd, Neighbourhood of high lands, or heated plains ; 4th, Rainfall 

 or clouds ; 5th, Ocean currents ; 6th, Prevailing winds. 



With respect to the present nature of the climate (apart from astro- 

 nomical causes), produced by physical or geological changes on the 

 earth's surface, Mr. Dowker dwelt on ' the exceptionally equable 

 character of that experienced in England. It was shown by the 

 isothermals of mean temperature, that Great Britain is milder than any 

 other country lying between the same parallels of latitude. 



It was mentioned that formerly every writer had agreed that the 

 present temperature of Great Britain compared with < ontinental 

 countries of the same latitude, was due to the gulf stream. The 



* Croll on the Changes of Climate in Geological Periods Phs. Mag., 1864. 



