PERIODICAL PHH NOMENA OF ANIMALS AND VEGETABLES. 325 
-vantageously supplied by the psychrometer, which is less liable to get out of 
order, and the indications of which are much more correct. 
We do not detail the precautions requisite for these observations, for 
which we merely refer to the ordinary treatises on physics. 
The force and direction of the winds should be carefully registered; as 
also the state of the sky. To indicate the degree of serenity, a decimal frac- 
tion may be employed; a perfectly serene sky being represented by unity, 
and one completely overcast by zero. By this mode of notation the inter- 
mediate states can be expressed in 10ths. 
The quantities of water falling, either as rain, hail or snow, should be col- 
lected by the aid of udometers, either immediately after their fall or at fixed 
times every 24 hours. 
The stormy, misty, &c. days should be noted. As to the state of the 
clouds, Howard’s system of notation may be advantageously employed. 
For those who are enabled to devote greater attention to the physical 
phenomena, we would recommend the observation of the electrical states 
of the air, of terrestrial magnetism, falling stars, aurore boreales, and earth- 
quakes; as also the temperature of springs, of plants and animals, as well as 
the analysis of waters and the air. But the latter is now in progress under 
the direction of M. Dumas, and we may expect the best results from labours 
directed by so practised-.a chemist. ‘The appreciation of the quantity of 
light and heat emanating from the sun, at different periods of the year and 
at various times of the day, has but little engaged the attention of philoso- 
phers, and deserves more notice. 
Lastly, to these living at the sea-side, the times and heights of the tides 
would be interesting subjects of observation. 
VEGETABLE Kincpom.—Observations relative to the vegetable kingdom 
may be regarded in two points of view, according as they bear upon the 
annual period or the diurnal period of plants. The annual period is that 
space of time comprised between two successive returns of the leaves, the 
flowers and the fruit; the diurnal period is the return of that hour of the day 
at which certain species of flowers open; for as all plants have fixed periods 
for their leafing and flowering, so in like manner certain species of plants open 
__ and close at certain hours of the day, and always at the same hours in the same 
_ place. The results presented by these phenomena are then of the greatest 
interest, not only to meteorology, but also to botanical geography. 
; In the study of them the principal object which ought to be aimed at is to 
_ vender the observations comparable, so that the results obtained on any given 
__ point may be compared with those of other countries. The essential point 
_. therefore does not consist in the large number of plants submitted to exami- 
nation, but in the choice of the species and the identity of the comparable 
conditions. 
\ It is with a view to the attainment of this object, that the following instruc- 
__ tions have been drawn up :— 
1. Observation for the annual period.—The first point in these observa~ 
_ tions is to discard annuals: in fact, these plants come up frequently at very 
various periods, according to the time at which they were sown, so that the 
indications furnished by them would not be comparable*. 
This consideration should also lead us to discard the use of biennials, be- 
~ Cause those which come up but slowly and towards autumn are necessarily 
__\' * M. Bergsma, president of the Horticultural Society of Utrecht, has however truly re- 
marked, that annuals might be usefully employed, provided precaution be taken to use in 
_ every case the same seeds and to sow them on the same days. 
\ 
