It is probable that some local
circumstances, perhaps the nature of the soil and the winds that
prevail in the flowering season, are the cause of this phenomenon.
In other regions, in the neighbourhood of Naples, for instance, the
coffee-tree thrives abundantly, though the mean temperature
scarcely rises above 18 centigrade degrees.
No person has ascertained in the island of Teneriffe, the lowest
height at which snow falls every year. This fact, though easy of
verification by barometrical measurements, has hitherto been
generally neglected under every zone. It is nevertheless highly
interesting both to agriculture in the colonies and meteorology,
and fully as important as the measure of the limit of the perpetual
snows. My observations furnished me with the data, set down in the
following table: -
Column 1: North latitude.
Column 2: Lowest height in toises at which snow falls.
Column 3: Lowest height in metres at which snow falls.
Column 4: Inferior limit in toises of the perpetual snows.
Column 5: Inferior limit in metres of the perpetual snows.
Column 6: Difference in toises of columns 4 and 5.
Column 7: Difference in metres of columns 4 and 5.
Column 8: Mean temperature degrees centigrade.
Column 9: Mean temperature degrees Reaum.
0 : 2040 : 3976 : 2460 : 4794 : 420 : 818 : 27 : 21.6.
20 : 1550 : 3020 : 2360 : 4598 : 810 : 1578 : 24.5 : 19.6.
40 : 0 : 0 : 1540 : 3001 : 1540 : 3001 : 17 : 13.6.
This table presents only the ordinary state of nature, that is to
say, the phenomena as they are annually observed. Exceptions
founded on particular local circumstances, exist. Thus it sometimes
snows, though seldom, at Naples, at Lisbon, and even at Malaga,
consequently as low as the 37th degree of latitude: and, as we have
just observed, snow has been seen to fall at Mexico, the elevation
of which is 1173 toises above the level of the ocean. This
phenomenon, which had not been seen for several centuries, took
place on the day that the Jesuits were expelled, and was attributed
by the people to that act of severity. A more striking exception
was found in the climate of Valladolid, the capital of the province
of Mechoacan. According to my measures, the height of this town,
situate in latitude 19 degrees 42 minutes, is only a thousand
toises: and yet, a few years before our arrival in New Spain, the
streets were covered with snow for some hours.
Snow had been seen to fall also at Teneriffe, in a place lying
above Esperanza de la Laguna, very near the town of that name, in
the gardens of which the artocarpus flourishes. This extraordinary
fact was confirmed to M. Broussonnet by very aged persons. The
Erica arborea, the Myrica Faya, and the Arbutus callicarpa,* (*
This fine arbutus, imported by M. Broussonnet, is very different
from the Arbutus laurifolia, with which it has been confounded, but
which belongs to North America.) did not suffer from the snow; but
it destroyed all the vines in the open air.
