Affricultnral Meteorology. 
3-27 
those plants most generally diffused over an extensive geogra- 
phical range. Schubler, who investigated this subject, concluded 
that, cfi'ten's jxiribus, every additional degree of latitude caused a 
delay of four days in the period of flowering. So that the same 
plant blossoming on a certain day at Parma would flower six 
davs later at Munich, thirteen at Tubingen, twenty-five at Berlin, 
thirty-three at Hamburg, and fifty-two at Christiania. But towards 
the Arctic Circle the greater duration of the summer day develops 
vegetation more quickly, and in fact the difference between 
Christiania and IJamburg is only three or four days instead of 
nineteen. 
Height also has its share in modifying heat. Schubler de- 
duced from his experiments in Saxony that every 98'26 feet 
caused the following delay in 
Flowering. Harvest. 
Days. Uavs. 
Wheat . . . 2-2 2-2 
Bailey ... 1-3 2-2 
Oats ... 2 2-2 
Potatoes . . 2-3 0-5 
But he observes that the same difference would not be found 
between a plain habitually covered with fog and a mountain per- 
fectly clear, or between a plain and a mountain equally clear.* 
many years must elapse belore we can deduce from them the mean rela- 
tions of one climate or latitude to another. 
From six years' observation, M. Qnetelet deduced the mean time for 
the flowering of the lilac at Biuxelles to be the 27th'5 of April ; but inthe 
course of those six years there was a difference of twenty days between the 
earliest (20th of April) and the latest (10th of May). In order to establish 
even an approach towards a basis, the number of years of observation 
ought at least to equal the term of the greatest divergence. In his ' Lettres 
sur Ic.s Probability's,' M. Quetelet has given a table (p. 248) of the flowering 
of the same plant for several other places ; but as yet the number of years 
is so small, that, as he himself admits, no great reliance can be placed on 
such a comparison. For instance, at Parma, from two observations in 1843 
and 1844, he fixes it for the 19th of April ; at Gand, from four years only, 
the 1st of May; at Prague, from four years also, the 10th of May; at 
Munich, from three years, the 10th of May. In the neighbourhood of 
Cambridge, from one observation, he fixes it for the 9th of May, or rather 
for ten days later than Biuxelles. Yet at Svvatt'ham in Cambridgeshire (see 
Farmers' Almanac for 1848), Mr. Jenkyns found, from a mean of ten years, 
that the lilac flowered there on the 30th of April, that is 2 days or 2-5 
days later than M. Quetelet's mean of Bruxelles. Swaffham is just four de- 
grees more to the north than Bruxelles. 
* Gasparin gives the following rule for calculating the decrease: — D, 
decrease ; t, temperature of the plains below ascertained ; t', that of space 
(-52^ Cent.) : then for the first 1000 metres (; ) D = ' ~ ' 
For tlie Asiatic continent we should have for 1500 metres D = 
t-t' 
2500 metres D = yy. 
