Under all circumstances they lie practically parallel, or nearly so, to the planet’s equator. It is generally thought that the planet, whatever may be its actual structure or constitution, is surrounded by a dense cloudy envelope, and that the shaded streaks which we call belts are rifts in this atmosphere, which expose to view the solid body of the planet underneath. Whether, however, the term “solid body” is an accurate one to be used in this connection is thought by some to be open to doubt. The laws which regulate the existence of these belts are quite unknown; indeed it seems doubtful whether any laws exist at all, for the belts at one time appear to undergo constant change, whilst at another time they remain almost unchanged for several months. It has been suggested that when the changes are rapid it must be presumed that great atmospheric storms are to be considered as in progress, and possibly this may be the true explanation. Belts are commonly non-existent immediately under the equator; whilst north and south of this void space it most usually happens that there is one broad belt and several narrower ones in each hemisphere. At each pole the planet’s brightness is less than the average brightness, but it cannot exactly be said that this is due to the existence there of belts properly so called. It was formerly considered that no tinges of colour could be traced on Jupiter except a silvery gray of different degrees of intensity; but during the last thirty years there can be no doubt that shades of brown, red, and orange, of no great depth, but yet quite definite have been traceable. Many observers concur in this opinion. Whether this detection of colour is due to an absolute development of colour during the period in question; or whether its detection is merely the result of more careful scrutiny with better instruments is a matter as to which the evidence is not clear. Though the general position of the belts is such that they are parallel to the planet’s equator, yet there are sometimes exceptions to this rule, for in a few very rare instances a streak in the nature of a narrow belt has been seen, inclined to the equator at a decided angle, perhaps 20° or even more.