84 Improvements in Physical Science [Ja 
lished in the Journal of the Royal Institution, i. 18S, that in Ma- 
racaybo, one of the provinces of Venezuela, 48 miles east of 
Merida, in about N. lat. 8°, and W. long. 70° and some minutes, 
there exists a small lake, from which a very considerable quantity 
of carbonate of soda is obtained once in two years. ‘The salt crys- 
‘tallizes at the bottom of the lake, and is obtained by diving. This 
lake, it would appear, is usually nearly saturated with the salt. It 
contains no animals whatever. 
VII. METEOROLOGY. 
1. New portable Barometer.—In the Ann. de Chim. et Phys. i. 
113, Gay-Lussac has proposed a new portable barometer, which 
seems entitled to considerable attention, as it may be made very 
light, is of easy execution, and of. course may be procured at a 
comparatively easy rate. It consists of a glass tube of the usual 
size, which continues cylindrical to A. (See Plate LX., Fig. 2.) 
Here a capillary glass tube is joined to it, whose internal diameter 
does not exceed one or two millimetres (0039 to 0°078 inch). This 
tube is bent upwards near its extremity, and united to a short tube 
of the same diameter as the upper part of the long tube. The 
short tube is shut at its upper extremity; but has a capillary hole, B, 
made in it, which allows a free entrance to the air without per- 
mitting the mercury to spill. Such is the outline of the con- 
trivance. It may be fitted up at pleasure, according to the fancy of 
the proprietor. 
The barometer of Gay-Lussac is a syphon one. Dr. Bischof, of 
Erlangen, has published (Schweigger’s Journal, xv. 387) a cheap 
method of constructing the common barometer, consisting of a 
straight glass tube plunged into a vessel containing mercury. He 
has also given a table of the correction of the length of the column 
of mercury for every degree of temperature. This is a correction 
that ought to be attended to in common meteorological observa- 
tions. I believe, if this correction were always made, that barome- 
ters in different places would be found to correspond with each 
other much more nearly than they appear to do at present. It is 
unnecessary to insert Bischof’s table here, as any person can easily 
construct a similar one for himself. 
2. A very remarkable phenomenon tock place at the town of 
Gerace in Calabria, on the 13th of March, 1813. The cireum- 
stance is related by Professor Sementini of Naples, and was pub- 
lished in the Bibliotheque Britannique ; but [ take it from the 
German translation published in Schweigger’s Journal, xiv. 130, 
The wind was westerly, and heavy clouds over the sea were 
approaching the land. About two hours after noon the wind fell, 
and the sky became quite dark. The clouds assumed a red and 
threatening appearance, thunder followed, and rain fell, which had 
a red colour from a mixture of red dust. The inhabitants were 
alarmed and flocked to the churches, conceiving that the end of the 
world was come. The red dust was very fine. It-became black 
