"The heat emitted by the sun, if used to melt a stratum of ice applied to the sun's surface would liquefy the ice at the rate of 2,400 feet an hour. It would boil per hour 700,000 millions of cubic miles of ice-cold water. Expressed in another form, the heat given out by the sun per hour is equal to that which would be generated by the combustion of a layer of solid coal 10 feet thick entirely surrounding the sun; hence the heat emitted in a year is equal to that which would be produced by the combustion of a layer of coal 17 miles in thickness. These are the results of actual measurements; and should greater accuracy be conferred on them by future determinations, it will not deprive them of their astonishing character. And this expenditure has been going on for ages, without our being able, in historic times, to detect the loss. When the tolling of a bell is heard at a distance, the sound of each stroke soon sinks, the sonorous vibrations are quickly wasted, and renewed strokes are necessary to maintain the sound. Like the bell, "Die Sonne tönt nach alter weise. "But how is its tone sustained? How is the perennial loss made good? We are apt to overlook the wonderful in the common. Possibly to many of us--and to some of the most enlightened among us--the sun appears as a fire differing from our terrestrial fires only in the magnitude and the intensity of its combustion. But what is the burning matter which can thus maintain itself? All that we know of cosmical phenomena declares our brotherhood with the sun--affirms that the same constituents enter into the composition of his mass as those already known to chemistry. But no earthly substance with which we are acquainted--no substance which the fall of meteors has landed on the earth--would be at all competent to maintain the sun's combustion. The chemical energy of such substances would be too weak, and their dissipation would be too speedy. Were the sun a solid block of coal, and were it allowed a sufficient supply of oxygen to enable it to burn at the rate necessary to produce the observed emissions, it would be utterly consumed in 5,000 years. On the other hand, to imagine it a body originally endowed with a store of heat--a hot globe now cooling--necessitates the ascription to it of qualities wholly different from those possessed by terrestrial matter. If we knew the specific heat of the sun, we could calculate its rate of cooling. Assuming this to be the same as that of water--the terrestrial substance which possesses the highest specific heat--at its present rate of emission, the entire mass of the sun would cool down 15,000° Faht. in 5,000 years. In short, if the sun be formed of matter like our own, some means must exist of restoring to him his wasted power. The facts are so extraordinary, that the soberest hypothesis regarding them must appear wild. The sun we know rotates upon his axis; he turns like a wheel once in 25 days: can it be the friction of the