on Job 38 :26
To cause it to rain on the earth - It is well known that rain falls copiously in thunder-storms. The flash is first seen, the clap is next heard, and last the rain descends. The lightning travels all lengths in no perceivable succession of time. Sound is propagated at the rate of 1142 feet in a second. Rain travels still more slowly, and will be seen sooner or later according to the weight of the drops, and the distance of the cloud from the place of the spectator. Now the flash, the clap, and the rain, take place all in the same moment, but are discernible by us in the succession already mentioned, and for the reasons given above; and more at large in the note on Job 36:29, etc. But how are these things formed? The lightning is represented as coming immediately from the hand of God. The clap is the effect of the lightning, which causes a vacuum in that part of the atmosphere through which it passes; the air rushing in to restore the equilibrium may cause much of the noise that is heard in the clap. An easy experiment on the airpump illustrates this: Take a glass receiver open at both ends, over one end tie a piece of sheep's bladder wet, and let it stand till thoroughly dry. Then place the open end on the plate of the airpump, and exhaust the air slowly from under it. The bladder soon becomes concave, owing to the pressure of the atmospheric air on it, the supporting air in the receiver being partly thrown out. Carry on the exhaustion, and the air presses at the rate of fifteen pounds on every square inch; see on Job 28:28 (note). The fibres of the bladder, being no longer capable of bearing the pressure of the atmospheric column upon the receiver, are torn to pieces, with a noise equal to the report of a musket, which is occasioned by the air rushing in to restore the equilibrium. Imagine a rapid succession of such experiments, and you have the peal of thunder, the rupture of the first bladder being the clap. But the explosion of the gases (oxygen and hydrogen) of which water is composed will also account for the noise. See below. But how does the thunder cause rain? By the most accurate and incontestable experiments it is proved that water is a composition of two elastic airs or gases as they are called, oxygen and hydrogen. In 100 parts of water there are 88 1/4 of oxygen, and 11 3/4 of hydrogen. Pass a succession of electric sparks through water by means of a proper apparatus, and the two gases are produced in the proportions mentioned above. To decompose water by galvanism: - Take a narrow glass tube three or four inches long; fit each end with a cork penetrated by a piece of slender iron wire, and fill the tube with water. Let the ends of the two wires within the tube be distant from each other about three quarters of an inch, and let one be made to communicate with the top, the other with the bottom of a galvanic pile in action. On making this communication, bubbles of air will be formed, and ascend to the top of the tube, the water decreasing as it is decomposed. The oxygen and hydrogen formed by this experiment may be recomposed into the same weight of water. Take any quantity of the oxygen and hydrogen gases in the proportions already mentioned; ignite them by the electric spark, and they produce a quantity of water equal in weight to the gases employed. Thus, then, we can convert water into air, and reconvert this air into water; and the proportions hold as above. I have repeatedly seen this done, and assisted in doing it, but cannot, in this place, describe every thing in detail. Now to the purpose of this note: the rain descending after the flash and the peal. The electric spark or matter of lightning, passing through the atmosphere, ignites and decomposes the oxygen and hydrogen, which explode, and the water which was formed of these two falls down in the form of rain. The explosion of the gases, as well as the rushing in of the circumambient air to restore the equilibrium, will account for the clap and peal: as the decomposition and ignition of them will account for the water or rain which is the attendant of a thunder storm. Thus by the lightning of thunder God causes it to rain on the earth. How marvellous and instructive are his ways!
on Job 38 :26
To cause it to rain on the earth, where no man is - This is designed to heighten the conception of the power of God. It could not be pretended that this was done by man, for the rain was caused to fall in the desolate regions where no one dwelt. In the lonely desert, in the wastes remote from the dwellings of people, the rain is sent down, evidently by the providential care of God, and far beyond the reach of the agency of man. There is very great beauty in this whole description of God as superintending the falling rain far away from the homes of people, and in those lonely wastes pouring down the waters, that the tender herb may spring up, and the flowers bloom under his hand. All this may seem to be wasted, but it is not so in the eye of God. Not a drop of rain falls in the sandy desert or on the barren rock, however useless it may seem to be, that is not seen to be of value by God, and that is not designated to accomplish some important purpose there.
on Job 38 :26
38:26 To cause - That the clouds being broken by lightning and thunder might pour down rain. No man - To water those parts by art and industry, as is usual in cultivated places.