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Dr. Young's Refractions, the Barometer being at 30 inches, and the inter

nal Thermometer at 50, or the external at 47, degrees; with the corrections for + one inch in the barometer, and for one degree in the thermometer of Fahrenheit. From page 19 of Vol. 1st of Pearson's Practical Astronomy.

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18,9 ,63 ,038 84 32,3 1,08 ,065 73 17,7 959,036 85 31,0 1,04,062 74 16,6 ,56,033 86 29,7 ,99,060 75 15,5 ,52,031 87 28,4 295,057|| 76 14,4 ,48 ,029 88 27,2 ,91,055) 77 13,4 ,45 ,027 59 25,9 987,052|| 78 12,3 ,41,025 90 24.7' ,83 1,050|| 79 11,21,38 1,023

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The correction for an increase of altitude of one inch in the barometer, or for a depression of one degree in the thermometer, is to be added to the tabular refraction ; but when the barometer is lower than 30 inches, or the thermometer higher than 50 degrees, the correction becomes subtractive.

When great accuracy is required, 0,003 inch should be deducted from the observed height of the barometer, for each degree that the thermometer near it, is above 50 degrees, and the same quantity added, for an equal depression.

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5.59 5.66 10 8.27 8.37 8.47 8.57 8.67 55 4.82 4.89 4.93

4.99

5.05 15 8.11

8.21

8.31 8.40 8.50 60 4.20 4.25 4.30 4.35 4.40 20 7.89 7.99 8.08 8.18 8.27 65 3.55 3,59 3.63 3.68

3.72 25 7.61 7.70 7.79

7.89 7.99 70 2.87 2.91 2.94 2.99 3.01 30 7.28 7.36 7.45 7.53 7.62 75 2.17 2.20 2.23 2.25 2.28 35 6.88 6.96 7.04 7.13 7.21 80 1.46 1.49 1.49 1.51

1.53 40

6.44 6.51 6.59 6.66 6.74 85 0.73 0.74 0.75 0.76 0.77 45 5.94 16.01 6.08

6.22 90 0.00 0.00 0.00 0.00 0.00 Logarithm for converting Sidereal into Mean Solar Time +9.9988126

Mean Solar into Sidereal Time + 0.0011874 A second of time, at the Equator, contains 1521 feet.

II. METEOROLOGICAL INFORMATION.

I. RED SNOW.*

Red Snow OF THE ALPS, OF THE Polar Regions, AND OF NEW SHET

LAND.

The ancients remarked that snow sometimes takes a red tinge, for we find in the works of Pliny (Book IX. ch. 35.) a passage in which it is stated that snow becomes red by age; Ipsa nix vetustate rubescit. The fact is at once announced and explained; such was the manner of the ancients, and by an extraordinary chance, this singular explanation is not without foundation. Several modern observers have directed their attention to this phenomenon. De Saussure saw red snow in the year 1760 on the Brévern, and in 1778 on the St. Bernard. (See Voyage dans les Alpes.") Haying described the position in which it lay, and all its phenomena, he gives it as his opinion, that this color is produced in the snow by vegetable dust. Ramond also found red snow among the Pyrenees. Captain Ross met with it on the shores of Baffin's Bay ; Captains Parry, Franklin, and Scoresby, in higher northern latitudes; and finally it has been found in great quantities by navigators in New or South Shetland, 70° south latitude.

The generous recluses of the St. Bernard, who in their meteorological observations display as praiseworthy a zeal as in their labors of charity, have frequent opportunities of seeing this red snow, and have collected it for the purpose of having it examined. By their means M. de Candolle has been enabled to make at Geneva a direct comparison between the coloring matter of the polar snow and that of the St. Bernard.

Among the Alps, red snow is found scattered here and there, generally in low places, or little sheltered hollows ; its depth not more than two or three inches at most, or rather, the zones in which it is found, though sometimes far beneath the surface, are generally not more than two or three inches in thickness.

On the shores of Baffin's Bay, Captain Ross collected red snow from a large hill five or six miles in extent. The summit of this hill was free from

* Translated from the Pouillet's Météorologie.

snow, and might be about 200 yards in height. Some of the learned men of the expedition seem to have thought that the red snow was found ten or twelve feet below the surface ; others, that its greatest depth might be only a few inches. This strange disagreement throws doubt on a point of some interest.

In order to analyze this extraordinary snow, it was put into flasks, and the melted water preserved from all contact with the air. The coloring matter seems to undergo no sensible alteration by time ; for the water, though limpid when quite tranquil, becomes red like the snow when its sediment is mingled with it by shaking the flask. We have accordingly been able to compare together the red snows of different countries.

Wollaston, R. Brown, De Candolle, Thénard, Peschier, and Francis Bauer have subjected this coloring matter to different trials for the purpose of determining its nature. Wollaston was the first to announce that it is composed of small spherical globules, whose variable diameters are comprehended between one two-thousandth and one three-thousandth of an inch. These globules have a transparent envelope, the interior being divided into 7 or 8 cells filled with a kind of red oil, not soluble in water. Messrs. R. Brown and De Candolle, having proved the existence of these globules, supposed them to be small plants of the alga or sea-weed family. Messrs. Thénard and Peschier have also satisfied themselves, by a chemical analysis, that this sediment in the melted water of red snow is of a vegetable nature.

Finally, Mr. Francis Baüer has published several memoirs on this subject, which seem to settle the question entirely. His first observations are of the same date with those of Wollaston, of which he had no knowledge. Mr. Baüer also has recognised the existence of the spherical globules and their separation into several compartments ; he has demonstrated that they are, in every respect, the same in the snows of New Shetland and in those of Baffin's Bay ; and he has classed these globules as little mushrooms of the genus uredo, forming a peculiar species which he calls uredo nivalis, because snow is their natural soil. Mr. Baüer has been led to this last opinion by an ingenious experiment; having exposed to the air the coloring matter, suspended in the melted water, he perceived at first that the microscopic globules were visibly multiplied ; but that these new-born individuals remained transparent. There was then in the water, a vegetation, but a vegetation incomplete ; it had not arrived at maturity. By substituting snow for water, during the winter months, this vegetation was seen to develope itself with greater success ; for the number of red globules was nearly doubled in a very short time, notwithstanding frequent interruptions from cold and snow.

These results seem to be decisive ; and they are at once so curious and so easily verified, that observers who are favorably situated should not lose the opportunity of satisfying themselves.

Snow on floating ice. Navigators who have visited the polar regions, have often observed red snow on floating pieces of ice. We should have presumed that the coloring matter in this case is derived from the same cause as in that of the continental snow; but Captain Scoresby, having observed, with a microscope, the sediment of these floating snows, believed that he perceived sensible and even rapid movements in the little corpuscles which constitute the coloring matter. It would seem then that there are two kinds of red snow, and two kinds of organized bodies capable of drawing nourishment from a soil apparently so ill suited to organic life. Though great confidence is due to the authority of Captain Scoresby, the animalcules, which he has described, bear so near a resemblance to the globules of the uredo nivalis, that it seems to us necessary to verify these results before they are adopted as decisive.

II. SHOWERS OF DUST, AND OF SOFT SUBSTANCES, BOTH

DRY AND LIQUID.

We shall refer to this head all the observations which have been made upon those extraordinary showers, called showers of blood, of ashes, of manna, etc., and of the various meteoric substances, soft or powdery, which fall from the atmosphere. To give an idea of the circumstances which sometimes accompany these meteors, we will take for an example the red shower which fell, on the 14th of March, 1813, in the kingdom of Naples and in the two Calabrias. M. Sementini has given the following description of this phenomenon.

“ On the 14th of March, 1813, an east wind having blown for two days, the inhabitants of Gerace saw a thick cloud spreading itself from the sea over the continent. At 2 o'clock in the afternoon the wind lulled : but the cloud already overhung the neighbouring mountains and began to intercept the light of the sun; at first it was of a pale red color, but afterwards deepened to a fiery red. At 4 o'clock in the afternoon the light was so obscured, that the inhabitants of the town were obliged to use candles in their houses. Many, terrified by the darkness and by the color of the cloud, went to offer public prayer in the churches. The darkness increased continually; thunder began to be heard, and the sea, though at the distance of six miles from the town, added its solemn voice. Then large reddish drops began to fall, which some supposed to be drops of blood, and others drops of fire. But, as night came on, the sky cleared up, the thunder ceased, and the people recovered their usual tranquillity.

« The same phenomenon of a shower of red dust took place, with some slight modification, not only in the two Calabrias, but in the opposite ex. tremity of the Abruzzi, without however causing any tumult among the people.

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