322 REPORT—1845. 
It is principally by the stmultaneity of observations made on a great number 
of points, that these researches are capable of attaining a high degree of im- 
portance. A single plant observed with care, would itself yield us information 
of the greatest interest. Synchronic lines might be traced on the face of the 
globe for its leafing, flowering, fructification, &c. The lilac, for example, 
Syringa vulgaris, flowers in the neighbourhood of Brussels on the Ist of 
May ; a line may be conceived on the surface of the earth upon which the 
flowering of this shrub takes place at the same date, as also lines on which 
its flowering is earlier or later by ten, twenty, or thirty days. Will those 
lines then be equidistant? will they have analogies with the isothermal 
lines? what will be the dependencies that will exist between them ?* so also 
as to the isanthesic lines or lines of simultaneous flowering, will these have a 
parallelism with the lines relative to the leafing, or to other clearly-marked 
phases in the development of the individual? We may conceive, for example, 
that whilst the lilac is beginning to bloom at Brussels on the 1st of May, 
there also exists a series of places northwards where this shrub is then only 
putting forth its leaves; has the line, then, which passes through these places 
any relations with the tsanthesic line which answers to the same date? It 
may also be asked whether the places that have the leafing on the same 
day, will likewise have the same day of flowering and fructification: it will 
thus be seen, keeping to even the simplest data, how many curious approxi- 
mations may be deduced from a system of simultaneous observations esta- 
blished on a large scale. The phenomena relating to the animal kingdom, 
those especially connected with the migrations of birds of passage, will afford 
results not less remarkable. \ 
Periodical phenomena may be divided into two great classes: the one be- 
long to the science of physics and natural history ; the others belong rather 
to the domain of statistics, and concern man living in the social state; for 
society itself, with all its tendencies to withdraw itself as much as possible 
from natural laws, has not been able to escape from this periodicity of which 
we are treating. 
The natural periodical pheenomena are in general independent of the social 
periodical phenomena ; but this does not hold good of these latter with regard 
to the former. It would therefore be a first step taken upon this ground so 
little explored, and which seems to promise so much to the labours of those 
who know how to cultivate it, to have commenced the simultaneous observa- 
tion of all the periodical phenomena connected with physics and natural 
history. 
These last phenomena are themselves divisible into several classes, and 
the study of them presupposes a considerable acquaintance with the meteoro- 
logical phenomena on which they principally depend. It is moreover not 
without reason that meteorology should take the lead, and commence this 
series of continued researches to which those observers who aspire truly to 
follow nature in all her laws of organization and development will have now 
to devote themselves. 
But meteorology, in spite of its persevering labours, has not hitherto been 
able to ascertain more than the mean state of the different scientific elements 
relating to the atmosphere, and the limits within which these elements can 
vary according to climate and season. It is requisite that it should continue 
its progress at the same time with the investigation now proposed; and in 
order to guide our judgement as to the observed results, it should show us, 
* Examples of similar researches have been given by Messrs. von Humboldt, Schouw, &e. — 
as to the boundary lines for the culture of the vine, olive, &c, in their relations with isother- 
mal lines, : r 
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