All specimens of these stones do not afford precisely similar results, but differ in their constituent elements and relative proportions; their component parts, however, are to be found abundantly in schist, schorl, pyrites, pebble, granite, &c. on which the sun must daily act. The following facts go to strengthen the above theory, viz. Meteors are most frequent and stupendous in tropical countries, where the heat of the sun is most intense; and less frequent in our climate in the winter and spring, while, and after the earth has been covered with snow for many weeks in succession; and they are most frequent in the higher latitudes towards autumn, after a continuation of hot dry weather: out of the whole number (179) of shooting stars I have noted during the last twelve years, 149 appeared between June and December, inclusive. If it be said that the specific gravity of meteoric stones being several times that of water, it is absurd to suppose they can rise, (if even reduced to the state of gas) to the elevated stations here assigned them, seeing the vapours of water can ascend only one or two miles above the earth. To this I reply, that the doctrine of heat is not yet so thoroughly understood, as to acquaint us with all its habitudes with natural bodies, but we infer from analogy, that the more refractory a body is in the fire, the greater in a due ratio is the absolute quantity of heat required to reduce it to, and retain it in, the state of gas, and the greater, in a corresponding degree, will be the dilatation of its particles and decrease of its specific gravity. Hence, if water reduced to vapour by heat, be capable of assuming an altitude of two miles, it follows that more refractory substances reduced to a similar state, will suffer expansion and fugacity in a due proportion to the quantity of caloric they employ, and will assume a corresponding elevation, as already inferred under my first head.