cially the movements of the sea under their influence, and the direction of their rotation. At what distance is the whirling motion of the air perceptible? What are the indications of the barometer during their approach and recess? Do any and what electrical phenomena accompany them? Does the water really ascend along their axis, and to what height? Is the water which they discharge in "bursting" fresh or salt? Note its temperature. Showers of Dust or Ashes.-When they fall, preserve specimens and examine them microscopically, whether consisting of organized or mineral matter. Note every circumstance, especially the direction of the wind, and whether an upper current, differing in direction from the lower, exist. The geographical situation of the ship especially should be exactly ascertained. Inquire for volcanic eruptions within a thousand miles of the place of their occurrence. Thunderstorms, Lightning, Fireballs, &c.-Note the quarter of the horizon where distant lightning unaccompanied with thunder appears, and the extent which it embraces. Especially notice any appearance of forked lightning striking upwards. In an actual thunderstorm, especially attend to the quantity of rain or hail that falls-its intermittences, and its correspondence or the contrary with great bursts of lightning near at hand. Notice the apparent direction taken by the storm, with or against the wind. Attend to the remarkable reversal in the direction of the wind which often immediately follows the cessation of a thunderstorm. Violent thunder and lightning in the immediate vicinity of the place of observation sometimes, though very rarely, take place without rain, or with very little. In such cases, notice every particular with the utmost minuteness, and ascertain, if possible, whether the storm has been elsewhere attended with rain. Fireballs are stated to have been occasionally seen running along the surface of the sea, and so reaching, striking, and "bursting" on ships-appearances which have been supposed analogous to the electrical phenomenon termed the glow discharge. Attend to every circumstance which may favour or oppose this idea, especially the height of the clouds at the time, and whether or no they are remarkably depressed along the line taken by the fireball. Should the ship be struck by lightning, if furnished with Sir Snow Harris's conductors (which appear to afford almost complete security against serious damage), examine the magnetism communicated to small steel bars (originally non-magnetic), fixed transversely across the copper conducting plates. Note any luminous appearance seen along the line of conduction. Immediately on the stroke, ascertain, by placing the hand on the conducting plate, whether it is in any degree heated. Notice peculiar noises, and endeavour to trace their origin, also the mode in which the lightning escapes from the ship, and the phenomena attending its escape. If damage be done, describe minutely the sort of effects produced, and endeavour to trace the direction and character of the forces immediately productive of such as are purely mechanical. Atmospheric Electricity can hardly be well studied at sea, the masts, sails, and rigging acting as perpetually interfering conductors. Indeed, it is said that, except in actual thunderstorms, no indications whatever of atmospheric electricity can be detected in the open ocean. This, however, should not be taken for granted. By going aloft the observer may put himself out of the reach of much of the interfering influence, taking with him an electroscope and a common jointed fishing-rod, having a glass stick well varnished with shellac substituted for its smallest joint to project into the atmosphere. To the end of the glass must be fixed a metallic rod terminating in a point, or carrying a small brass lantern, in which a lamp is burning, and connected with the electroscope by means of a fine copper wire. The electroscope may be either Saussure's pith ball, or Singer's * For the infinitely varied ways in which lightning may affect a ship when struck we recommend a perusal of Sir S. Harris's short but interesting work, 'Remarkable Instances of the Protection of certain Ships from the Destructive Effects of Lightning, &c.,' London, 1847. gold leaf electrometer, and when charged the nature of the electricity may be tested by excited glass or sealing wax. Auroral Phenomena.-All such should be minutely registered, and all their phases, especially the formation, extent, situation, movement, and disappearance of arches, or any definite patches or banks of light. An acquaintance with the principal stars of the constellations is necessary to observe such phenomena with effect, and the observer will do well to provide himself for the purpose with planispheres, on which only the more conspicuous stars are indicated, with their allineations. The exact time (true at least to the nearest minute) of any such definite body of light being centrally on any known star should be observed, as a means (by the aid of corresponding observations) of determining its real situation and altitude. The slow drifting motion of such masses (in north latitudes generally southward-query if the reverse in south?) should be specially attended to. Pulsations, like waves of light, rushing up from the horizon, should be also particularly remarked, and any appearance of patches of definite forms rendered visible by such pulsation as it traverses them, but not otherwise appearing as luminous masses, particularly noticed. When arches or any considerable well-defined cloud-like masses are. formed, mark on the chart their situation and extent among the stars at several noted epochs of time, particularizing the brightest portions; observe also the point of convergence of streamers and the formation of the corona, the central point or focus of which should be projected on the chart with all possible exactness, and the time of so doing exactly taken, so as to determine by subsequent calculation its altitude and azimuth. Any indication of the near vicinity of auroral phenomena, or of their existence at a level below that of ordinary clouds, should be most minutely investigated at the moment, and carefully and circumstantially recorded. The connexion, if any, between auroral masses and cirrous clouds should be traced if opportunity occur. Note also the meteors if remarkable within the auroral region. M Halos, parhelia, mock suns, and other luminous phenomena of the kind, should be noted, delineated with care if complicated, and their dimensions measured with a sextant or other instrument, by bringing the limb of the sun or moon (noting which limb) in contact with the two edges of the phenomenon in succession. Their colours also and their order should be described. Light cirro-stratus cloud in the neighbourhood of the sun has been observed to be bordered with three fringes of pink and green colours following the outline of the cloud. This rare and beautiful phenomenon if seen should be most particularly and carefully described. Perhaps in some climates it may be of not unfrequent occurrence. Unusual tints observed in the sky should be noted; and should that extremely rare phenomenon-the sun's disc appearing of a pale blue colour, so little luminous as to allow of being gazed at with impunity*-occur, the atmospheric circumstances should be carefully recorded. The polarization of the light of the sky should be examined habitually with a polariscope, and the relation of the points of maximum polarization to the sun, and the observer's zenith, noticed in every variety of climate, and in various states of the sky, and anything apparently abnormal recorded. Zodiacal light. In the seasons of its appearance take every opportunity in tropical climates to ascertain with precision the place of its apex among the stars, its breadth and degree of brightness, and whether variable or not. Meteors. See Article I., Astronomy-Appendix I. *It occurred at Bermuda on the 12th and 13th of August, 1831, two days after the great Barbadoes hurricane of that year. |