fairest weather, and devour all the corn of that country; laying their eggs in autumn, and then dying; but the eggs, of which every one lays two or three hundred, hatching the next spring, produce again such a number of locusts, as to be far more destructive than before, unless rains fall, which kill both eggs and the insects themselves, or unless a strong north or north-west wind arise, which drives them into the Euxine sea.

Observations on the Barometer. By Dr. WALLIS.

[1666.]

THE Doctor never observed the quicksilver higher than 30 inches, nor lower than 28, at least within of an inch of these numbers, either over or under.

In thick foggy weather, he found the quicksilver rise; which he ascribes to the heaviness of the vapours in the air. In sun-shiny weather it rises also, and commonly the clearer the weather the higher it is; which may be owing partly to the vapours raised by the sun and increasing the weight of the air; partly to the heat which adds to the elasticity of the air; which latter he mentions, because in sunshiny weather, which became afterwards cloudy for an hour or two, the quicksilver has fallen; and then on the sun's breaking out again, it has risen as before.

In rainy weather it falls, because the air is light in proportion to the quantity of vapours that falls; and also in snowy weather, but not so much as in rain; and sometimes it has fallen upon a hoar-frost in the night.

In windy weather it generally falls, and more discernibly than in rainy, owing possibly to the wind's moving the air laterally; and thereby preventing its pressure downwards; and he never found it lower than in high winds.

He observed the quicksilver fall without any visible cause, but upon looking abroad, he found it had rained at some distance; whereby the heavier air might have in part discharged itself on the lighter.

The Rotation of Jupiter on his Axis. By Mr. Hook and M. Cassini.[1666.]

ABOUT nine o'clock at night, May 9th, 1664, Mr. Hook observed, with a good 12-foot telescope, a small spot in the largest of the three obscurer belts of Jupiter; and, observing it from time to time, he found that within two hours after,

the said spot had moved from east to west, about half the length of the diameter of Jupiter.

According to M. Cassini there are two sorts of spots to be seen in the disk of Jupiter; the one being only the shadows of his satellites, the other sort resembling those that are seen in the moon; and they are perhaps of the same nature with those called belts. They move from the eastern to the western limb; their apparent motion is unequal, and swifter near the centre than the circumference; and they are never seen so well as when they approach the centre; for in approaching the circumference they become very narrow, and almost imperceptible; which seems to argue that they are flat and superficial.

Among these spots, there is none so observable as that situated in the northern part of the southern belt. Its diameter is of Jupiter's; its centre when nearest is distant from that of Jupiter about of the semidiameter of that planet.

M. Cassini, after many observations during the summer of 1665, found that the period of its apparent revolution is 9 hours 56 minutes. He continued to observe this spot till the beginning of 1666, when Jupiter approached to the beams of the sun; but after he got out of them it was difficult to be discerned.

General Heads for a Natural History of a Country. By Mr. BOYLE.[1666.]

THE things to be observed in such a history may be variously divided: as into supraterraneous, terrestrial, and subterraneous.

1. To the first sort of particulars belong the longitude and latitude of the place, and, consequently, the length of the longest and shortest days and nights, the climate, the parallels, &c.; what fixed stars are, and what are not seen there.

2. Concerning the air, may be observed its temperature, as to the first four qualities and the measures of them: its weight, clearness, refractive power; its subtilty or grossness; its abounding with or wanting salts, its variations according to the seasons of the year, and the times of the day; what duration the several kinds of weather usually have; what meteors it mostly produces, and in what order they are generated; and how long they usually last; especially, what winds it is subject to; whether any of them be stated and

ordinary, &c. What diseases are epidemical; what is the usual salubrity or insalubrity of the air; with what constitutions it agrees better or worse than others.

3. Concerning the water, may be observed the sea, its depth, degree of saltness, tides, currents, &c. Next rivers, their width, length, course, inundations, goodness, lightness of waters, &c. Then lakes, ponds, springs, and especially mineral waters, their kinds, qualities, virtues, and how examined. To the waters belong also fishes, their kinds, whether salt or fresh water fish; their quantity, size, goodness, seasons, haunts, peculiarities of any kind, and the ways of taking them, especially those that are not purely mechanical,

4. In the earth may be observed,

1. Itself. 2. Its inhabitants and its productions, both external and internal.

First, In the earth itself may be observed, its dimensions, situation, east, west, north, and south: its figure, its plains and valleys, and their extent; its hills and mountains, and their height; and whether they lie scattered or in ridges, and in what directions they run, &c. What promontories, fiery or smoking hills, &c. What the magnetical declination is in several places, and the variations of that declination in the same place: what the nature of the soil is, whether clay, sandy, &c. or good mould; and what grains, fruits, and other vegetables, do the most naturally agree with it: also, by what particular arts the inhabitants improve the advantages and remedy the inconveniences of their soil?

Secondly, There must be given a careful account of the inhabitants themselves, particularly their stature, shape, colour, features, strength, agility, beauty, complexions, hair, diet, inclinations, and customs. Of the women, there may be observed their fruitfulness or barrenness, their hard or easy labour, &c. What diseases both women and men are subject to, and unusual symptoms attending them.

Ås to the external productions of the earth, the inquiries may be such as these: What grasses, grains, herbs, flowers, fruit-trees, timber-trees, coppices, groves, woods, forests, &c. What peculiarities are observable in any of them: what soils they best thrive in. What animals the country has, either wild or tame.

The internal productions or concealments of the earth, are here understood to be the riches that lie hid under the ground, and are not already referred to other enquiries: what sorts of minerals and quarries the country affords, and

the particular conditions both of the quarries and the stones: also, how the beds of stone lie, in reference to north and south, &c. What clays and earths it affords, as tobacco pipe-clay, marls, fullers' earths, earths for potters' wares, boluses, and other medicated earths: what other minerals it yields, as coals, salt-mines, or salt-springs, alum, vitriol, sulphur, &c. What metals the country yields, and a description of the mines, their number, situation, depth, signs, waters, damps, quantities of ore, goodness of ore, extraneous things, and ways of reducing their ores into metals,

&c.

Of four Suns observed in France.-[1666.]

On the 9th of April, 1666, about half an hour past nine, there appeared three circles in the sky. One of them, schn (see engraving), was very large, a little interrupted, and white every where, without the mixture of any other colour. It passed through the middle of the sun's disk, and was parallel to the horizon. Its diameter was above 100 degrees, and its centre not far from the zenith a.

The second, debo, was much less, and deficient in some places, having the colours of a rainbow, especially in that part which was within the great circle. It had the true sun for its centre.

The third, hd n, was less than the first, but greater than the second it was not entire, but only an arch or portion of a circle, whose centre was far distant from that of the sun, and whose circumference about its middle d was joined to that of the least circle, intersecting the greatest circle at its two extremities hn. In this circle were discerned also the colours of a rainbow, but they were not so strong as those of the second.

At the part where the circumference of this third circle closed with that of the second, there was a great brightness of rainbow-colours mixed together: and at the two extremities, where this second circle intersected the first, appeared two parhelias or mock suns hn; which shone very bright, but not so bright or so well defined as the true sun. The false sun h, towards the south, was larger, and far more luminous than that towards the east.

Besides those two parhelias which were on the two sides of the true sun, in the intersection of the first and third circle, there was also upon the first great circle a third mock sun c, situated to the north, which was less and less bright than the two others. So that at the same time there were seen four suns in the heavens. There was also a very dark space between d and r.

This appearance is considered as one of the most remarkable that can be seen, by reason of the excentricity of the circle hdn, and because the parhelia were not in the intersection of the circle debo with the great circle schn, but in that of the semicircle hdn. Which are different from the position of those five suns seen at Rome on March 29. 1629, between two and three o'clock A. M., two of them appearing in the intersection of a circle passing through the sun's disk, with another that was concentric with the sun, as in the engraving.

Hypothesis on the Flux and Reflux of the Sea. By Dr. JOHN WALLIS.[1666.]

THE sea's ebbing and flowing has so great a connexion with the moon's motion, that all philosophers have attributed much of its cause to the moon, which either by some occult quality, or particular influence which it has on moist bodies, or by some magnetic virtue, drawing the water towards it, which should therefore make the water highest where the moon is vertical, or by its gravity and pressure downwards upon the terraqueous globe, which should make it lowest, where the moon is vertical, or by whatever other means, has so great an influence on, or at least connexion with, the sea's flux and reflux, that it would seem very unreasonable to separate the consideration of the moon's motion from that of the sea: the periods of tides, to say nothing of the greatness of them near the new and full moon,