328 
A(jricuUural Meteorology. 
The mean decrease of temperature observed on an average of 
five aerial voyages (mcluding; the celebrated ascent of Gav-Lussac 
,to the height of 22,632 feet) has been 1° Fahr. for every 3G0 
feet of elevation. 
In the south of Germany and north of Italy every 310 feet 
causes a decline of 1° Fahr. ; in the United States it is 404 feet, 
in Siberia 440 feet. 
Before quitting the subject of heat, it may be as well to remark 
the extraordinary halt in the increase of the temperature between 
the 10th and 13th of February, and again fro^n the 8th to the 
13th of May, which has been noticed in France as well as in 
England, and there attributed to the intervention of asteroides 
between the sun and earth during those periods. 
There is also little increase of heat from the 25th of March to 
the 15th of April at Paris, but thenceforward the rise is irre- 
gular; the curve of the descent of temperature in the autumn is 
much more uneven than that of its ascent in the spring. There 
appear to be two maxima of heat, one at the beginning, the other 
at the end of July, owing, probably, to that month being generally 
showery, which of course have their effect in lessening its warmth. 
M. Gasparin would make the middle of winter coincide with 
the coldest period of the year, and that of summer with the 
hottest. Our seasons do not do so according to their present 
nominal distribution. The mean maximum of cold occurs at 
Paris, as at London, about the middle of January. Taking that 
as the centre of winter, he would assign the 1st of December as 
the commencement of that season — the 1st of March for that of 
spring — thus making each coincide with three calendar months. 
This would be a less inconvenient change than that })roposed by 
Mr. Luke Howard, who would have all our seasons commence 
fifteen days earlier than the equinoxes and solstices. Winter, 
then, by his scheme, would begin on the 7th of December, lasting 
to March 5th, during which time the mean daily temperature in 
the neighbourhood of London will have fallen from 39 
(Fahrenheit) to 34*55', rising again to 39 •94". The vernal 
quarter occupying ninety-three days to June 6th, would have 
risen 18' 14°, to a temperature of 58-8'. 
Summer would rise to 64 75^ declining to 58' 16' by the 7th 
of September, when the autumn would begin. During the three 
next months the temperature would decline 18 •35°, the same 
number of degrees, within a small fraction, that it rose in the 
spring. 
This division might introduce some perplexity into our calendars, 
but it is no doubt more exact and methodical than our present 
arbitrary derangement of nature. The mean greatest cold and 
the mean greatest heat would then form the centres of the winter 
