our knowledge both of the phenomena which take place in the regions of the atmosphere, and of the powers of nature which operate in their production.

With respect to the aurora boreales, some data might be ascertained for determining their height above the surface of the earth, which might lead to a discovery of their true cause, were a multitude of observers, in different places, at the same moment, to take the altitude and bearing of any particular coruscation, particularly of the modification of this phenomenon which assumes the form of a rainbow or luminous arch, which can instantly be done by noting the series of stars which appear about the middle or sides of the arc at any particular instant. By this means the parallactic angle might be found, and the distances of the places of observation, or their difference of latitude, if directly north and south of each other, would form base lines for determining the perpendicular elevation of the phenomenon. In reference to luminous meteors, as they are most frequently seen in the night-time, men of science and persons of elevated rank have seldom opportunities of observing their diversified phenomena, and the circumstances with which they are preceded and accompanied. But while persons of this class are reclining on beds of down, or regaling themselves at the festive board, hemmed in from the view of the surrounding sky by the walls and curtains of their splendid apartments, many in the lower walks of life are "keeping watch by night," or travelling from place to place, who have thus an opportunity of observing every variety of atmospherical phenomena; and it is not unlikely may have seen several species of luminous and fiery meteors unknown to the scientific world. Were persons of this description, particularly watchmen, soldiers, sailors,

mail-coach-guards, policemen, and such like, capable of observing such appearances with scientific interest and accuracy, and of recording their observations, various important additions might be made to the facts which compose the natural history of the atmosphere.

Similar additions might be made to our knowledge of thunder storms, were their phenomena and concomitant circumstances accurately noted by a vast number of persons in different places. It might, for example, be determined, from a multitude of observations made with this special object in view,-at what distance from the earth a thunder-cloud may explode without danger?-in what circumstances, and at what elevation it generally attains its striking distance, and brings us within the range of its destructive influence ?-what particular effects, hitherto unobserved, are produced by lightning on animal, vegetable and mineral substances ?-to what practical purposes its agency might be applied,—and how its destructive ravages might be averted or diminished? The same remarks will apply to the singular phenomenon of meteoric stones. These have seldom. been observed at the instant of their descent by men addicted to philosophical research; but chiefly by peasants, labourers, and mechanics, who, at present, are generally unqualified for attending to every circumstance in the preceding and concomitant phenomena connected with their descent, with the discerning eye of a philosopher; and therefore, we may still be ignorant of certain important facts in the history of the fall of these bodies, which may long prevent us from forming any rational theory to explain their causes, or to determine the regions whence their origin is derived.

Astronomy.-My next illustration shall be taken from the science of astronomy. Though this is among the oldest of the sciences, and its general principles are established with greater precision than those of almost any other department of science, yet many desiderata requisite to its perfection, still remain to be ascertained. The late discovery of several new planets, both primary and secondary, leads us to conclude, that other globes of a similar nature, belonging to our system, may still lie hid in the distant spaces of the firmament. The spheroidal figure of some of the planets-their periods of rotation— the nature of the changes which appear to take place on their surfaces or in their atmospheres-the precise nature of the solar spots, the causes of their changes, and the influence which those changes produce on our earth or atmosphere-the parallax of the fixed stars-the rate of motion of the planetary system in absolute space-the gradual formation or Nebula-the nature of variable stars-the number of comets, their periods, the nature of their tails and atmospheres, and their uses in the system of nature— with many other interesting particulars of a similar description, still remain to be ascertained. To determine such objects, requires a multiplicity of longcontinued observations in every region of the heavens; and, it must be evident, that the more we increase the number of astronomical observers, the greater chance we shall have of acquiring a more accurate and comprehensive knowledge of the bodies which roll in the distant regions of the universe, and of the relations they bear to one another, and to the whole system of nature.

This position might be illustrated by a few examples. The surface of Jupiter has been found to be

diversified with a variety of spots and belts: the belts, which are considerably darker than the general surface of the planet, are observed to vary in their number, distance, and position. Sometimes only one or two, and sometimes seven or eight belts have been observed; sometimes they are quite distinct, and at other times they seem to run into each other; and, in some instances, the whole surface of this planet has appeared to be covered with small curved belts that were not continuous across his disk.

The following figures represent some of the diversified views which Jupiter sometimes exhibits.

be one of the views of this planet taken by the celebrated Cassini. It consists of about nine different belts. Fig. 2, is copied from Schroeter, and exhibits a view of Jupiter about the time of its occultation by the moon, on the 7th of April 1792. Fig. 3, is one of Sir W. Herschel's views of this planet, as it appeared on the 28th May 1780, when the whole disk of Jupiter appeared covered with small curved belts, or rather lines, that were not continuous across his disk. Fig. 4, contains a view which is nearly the appearance which Jupiter exhibits at present, and which is not much different from his appearance for several years past. These appearances may be seen by a good Achromatic telescope, magnifying from 80 to 150 times. These views demonstrate, that changes of considerable magnitude are occasionally taking place, either on the surface or in the atmosphere of this planet, which it would be of some importance to ascertain, in order to our acquiring a more intimate knowledge of the physical constitution of this globe. Now, were a number of observers, in different places, to mark these appearances, and to delineate the aspect of this planet during the space of two or three periodical revolutions,* marking the periods of the different changes, and noting at the same time the positions of his satellites-it might be ascertained, whether these changes are occasioned by tides, which are differently affected according to the position of his moons, or, by immense strata of clouds, or other changes that take place in his atmosphere, or by some great physical revolutions which are occasionally agitating the surface of this planet. The

* The annual or periodical revolution of Jupiter is completed in about eleven years and ten months.