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True Apparent Places of Thirty-seven of the Principal Fixed Stars for every

Tenth Day of the Year.
Epoch. — The Upper Culmination at Greenwich.

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EF Right Asc.

O Dec. North.

44

21

21

22

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O 1855.

20
m. s.
m. S.
m. S.
m.

m. 8. Jan. 1 36 26.90 45 49.5 15 3.83 58 23.1 58 18.40 i 30.1 49 36.35 23 39.5 57 30.97 25 30.4 11 26.85 46.6 3.62 20.4

18.36 30.9 36.27 39.1 30.88 29.3 21 26.86 43.7 3.48 17.4 18.35 31.7 36.21 38.4 30.81 28.1 31 26.92 40.4 3.41 14.2

18.37 32.3 36.18 37.4 30.77 26.8 Feb. 10 27.02 37.4 3.43 10.7 18.41 32.9

36.18 36.2 30.75 25.6 20 27.18 34.7 3.54 7.5 18.50 33.3 36.21 34.7 30.76

24.4 Mar. 2 27.38 32.3 3.73 4.6 18.61

33.5 36.28 32.9 30.80 23.4 12 27.63 30.4 3.99 1.9 18.75 33.4 36.391

31.01 30.89 22.5 22 27.92 28.9 4.33 57 59.7 18.93 33.1 36.53 29.0

31.00

21.9 Apr. 1 29.24 27.9 4.73 58.0 19.13 32.6

36.71 26.8 31.16 21.7 11 28.58 27.6 5.18 56.9 19.37 31.7 36.93 24.5

31.35 21.8 21 28.95 27.8 5.66 56.4 19.63 30.6

37.19

22.2 31.57 22.3 May 1 29.32 28.6

6.17

56.5 19.92 29.2 37.48 19.9 31.83 23.1 11 29.70 29.9

6.69

57.3 20.22 27.6 37.79 17.7 32.12 24.2 21 30.06 31.8 7.21 58.6 20.53 25.8

38.13 15.5 32.43 25.7 31 30.41 34.) 7.70 58 0.5 20.85 24.0 38.49 13.5 32.75

27.4 June10 30.73 36.8

8.16

2.8 21.17 22.0 38.86 11.7 33.07 29.4 20

31.01 39.7 8.53 5.6 21.48 20.1 39.22 10.1 33.40 30 31.26 42.9

8.7 21.76 18.1 39.57 8.9 33.71 33.8 31.15 46.2 9.22

12.0
22.02 16.3 39.90 7.9 34.00

36.2
20 31.59 49.5
9.44 15.6 22.25 14.6 40.20

34.27 38.5 30 31.67 52.8 9.58

19.2 22.44 13.0 40.47 7.0 34.51 40.8 Aug. 9 31.69 56.0 9.63

22.9
22.60 11.6 40.70

7.1 34.71 43.0 19 31.66 59.1 9.61 26.1 22.71 10.5

40.89 7.5 34.87 45.1 29 31.58 46 1.8 9.51 29.9 22.77

9.6 41.02 8.2 34.98 47.0 31.44

4.3 9.33 33.1 22.79 8.8 41.10 9.1 35.06 48.7 18 31.26 6.5 9.09

22.77 8.3

41.14
10.3 35.09

50.2 28

8.3 8.79 38.6 22.72 8.1 41.13 11.6 35.09 51.4 Oct. 8 30.91 9.6 8.14 40.8 22.61 8.0 41.08 12.9 35.06 52.4 18 30.56 10.5 8.06 42.6 22.54 8.0 41.00

14.3 34.99 53.1 30.30 10.9 7.65 43.8 22.42 8.3 40.89 15.6. 34.91

53.6 Nov. 7 30.04 10.8 7.22 44.5 22.29 8.6

40.76 16.8 34.81 53.8 17 29.79 10.2 6.79

44.6
22.17 9.1

40.62

17.9 34.69 53.8 29.56 9.1 6.38

49.2
22.05 9.7 40.48 18.7

34.58

53.5 Dec. 7 29.37

7.5
6.00 43.2 21.94

10.4 40.31 19.2 34.46 53.0 17 29.21

5.5 5.65 41.6 21.85 11.1 40.21 19.5 34.34 52.3 27 29.09

5.35
39.5 21.78

11.9 40.16 19.5 34.24 51.4 37 29.02 0.4 5.10 37.0 21.741 12.61 40.00 19.2 34.15

50.4

31.6

8.94

July 10

7.3

Sept. 8

36.0

31.05

28

27

3.1

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

Thermometer at 50, or the external at 47 degrees ; with the Corrections for + one inch in the Burometer, and for one degree in the Thermometer of Fahrenheit. From page 19 of Vol. I. of Pearson's Practical Astronomy.

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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 47 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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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.

ATMOSPHERICAL ELECTRICITY.

By Professor Joseph Locering of Harvard University. In the last volume of this Almanac, I gave an exposition of the electrical states of the earth and its atmosphere; of the ways in which these electrical states are produced, and the various methods contrived for studying them. I propose in the present or the next volume to add some remarks on the physical cause of thunder and lightning, considered as the visible tokens of electric discharge ; on the danger of being struck by lightning ; on the protections against it, natural and artificial, which have been provided by Providence or human agency; on lightning-rods, and their efficacy; and on the effects which electricity may possibly produce when and where it chances to strike.

Aristotle speaks thus of the phenomena to be discussed: “We, however, say that the same nature upon the earth is wind, but in the earth is an earthquake, and in the clouds is thunder.""* Aragot has defined thunder and lightning as a phenomenon or meteor which is exhibited when the heavens are covered with clouds; and which manifests itself first by light and then by noise. I will not dwell upon the fanciful distinctions on this subject made by the Etruscans, renowned as they were in the ancient world for their knowledge of these things. Pliny divided lightnings into public and private. He also distinguished between those which came from the stars and those which rise out of the earth. But Aristophanes, in the Clouds, ridicules the idea that thunder ever comes from the earth.

Regarding thunder and lightning as an atmospheric phenomenon, revealing to man's senses the violent discharge of electricity between one cloud and another, or between the earth and a cloud, I proceed first to inquire into the peculiarity and height of thunder-clouds. Arago mentions, as one peculiarity, a kind of fermentation, which Forster compared to that of cheese when full of maggots. Peytier and Hossard, while engineering upon the Pyrenees, observed that, even when the clouds were smooth underneath, they were often rough above.

The effects of the lightning's stroke have been found on the highest mountains. Humboldt recognized them in South America ; Saussure discovered them on Mont Blanc; Ramond, Peytier, and Hossard met them on the summits of the Pyrenees; and Bouguer and Condamine on the Cordilleras. But it is not safe to presume that thunder-clouds reach as high as the effects of their explosion. For the lightning may strike from a lower cloud up to a higher peak as well as downward. There is a church in Styria, standing upon a prominent mountain-top. On May-day, 1700, a physician at that place noticed a dense black cloud below him; the sky above was a clear blue, when a flash of lightning ascended from the cloud, struck the church, and killed seven persons. Murray says he has seen lightning ascend in a spiral line.

But even if it were admitted that the height of thunder-clouds is coequal with the marks of lightning, it would still be necessary to inquire whether thunder-clouds rise to that height in level countries. To answer this question, resort is had to an observation of the interval which elapses between the flash and the report. But unless the angular elevation of the cloud above the horizon is recorded, and is taken into the account, the observation gives, and can only give, the distance of the cloud from the observer, and not its perpendicular elevation above the earth's surface. And this distance is correct only on the supposition that the sound is made in the cloud, and not along the whole line of discharge. Subject to these corrections, a large number of illustrative cases, compiled by Arago, may

* V. 535.

Annuaire, 1838.

*

be used to answer the question in regard to the height of thunder-clouds, and to show an extreme height of 26,500 feet. On the 5th of July, 1788, Saussure and son had a thunder-storm above them, although their tents were pitched in one instance 3,471 metres, and in another 4,500 metres, above the level of the sea. On one occasion, Massena and Suwarrow were fighting a battle on the St. Gothard in clear sunlight, while nature's artillery, in the shape of a thunder-storm, was exploding below them. If, therefore, the effects of lightning, and lightning itself

, are known to exist on high mountains, and even above their surface, frequently, if not generally, thunder-clouds are much nearer the sea, and sink often to distances not exceeding 1,000 feet above the earth’s level surface.

Aristotle, Lucretius, Pliny, and Seneca, all have sought curiously into the nature of lightning. Seneca says: “ Fire is produced by the percussion of flint and steel, or by the friction of two pieces of wood. It may happen, therefore, that the clouds, hurried away by the wind, are likewise inflamed by means of percussion and friction."

The Clouds of Aristophanes embodies the same idea.

Lightning and thunder are the momentary effects produced by the passage of atmospherical electricity, as the common electrical spark and snap betray the ordinary discharge of electricity from an artificial electrical machine. It is not necessary, therefore, in this connection, to ask how or why it is that the light marks the path of the lightning so plainly, that this effect has come even to designate the cause which produces it.

The flashes of lightning which we see are indications of the passage of electricity, sometimes between a cloud and the earth, but more frequently from cloud to cloud. Gay-Lussac determined the length of the flash to be sometimes three miles in extent. The electricity is restrained upon a cloud as upon the prime conductor of an electrical machine, not by the pressure of the air, but by its non-conducting character. When it is considered that a large prime conductor will not collect and retain electricity sufficient to give a spark more than two or three feet in length, it is wonderful, if not inexplicable, how the lightning can dart from the cloud over such spaces. Leslie # believed it to be carried, by a process analogous to the convection of heat, by the vapor itself in its descent. If it is not carried by convection, but by common conduction, the particles of moisture or rain may compose a chain of communication from point to point. Hence the lightning strikes to the ground more easily after rain; and whenever it strikes before rain, it is because it has extraordinary force, and so on such occasions it causes unusual havoc. Gay-Lussac makes a distinction between electricity on a cloud and electricity on the prime conductor of an electrical machine.

An interesting question may be started at this stage of the inquiry, viz. whether lightning always starts from the cloud towards the earth, and never leaves the earth to go to the cloud. It would be impossible to answer this question, either in regard to lightning or artificial electricity, by direct observation, because the fluid passes so rapidly over the longest spaces that its whole track will be illuminated at once. Still, individuals think sometimes they can see the flash start, and sometimes start first from the earth. Kaemtz saw the spark leave two clouds and unite in the middle. I am inclined to explain these results as subjective phenomena. If, for any reason, one part of the flash is brighter than the other, it will require less time to make its impression upon the eye. Now, I have recently seen flashes which appeared the brightest at the lower end, because the upper was partially veiled by a cloud. And often the two cxtremities of an electrical spark are brighter than the middle.

But the direction in which bodies have been scattered by lightning has

* Quæst. Nat., Liv. II. $ 22.
| Edin. New Phil. Journ., XI. 1824, pp. 26, 27.

Ann. de Ch. et Phys., XXIX. 105. s Ann. de Ch et Phys., XXIX. 105.

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