He has learned to control the mechanical, chemical, and electric forces. When he lifts a stone from the earth and suspends it in the air, or locks it in the arch that spans the river, the law of gravitation is subordinated to the higher law of intelligent purpose. By the collocation and adjustment of mechanical forces he overcomes the resistance of winds and tides, and guides his vessel across the trackless deep. He seizes the lightning in the clouds and guides it harmless to the earth, and sends the electric current along the telegraphic wire to chronicle his deeds and report his thoughts at the ends of the earth. He loosens the most intricate combinations of elementary substances, and recomposes them in new forms of the highest value in medicine and the fine arts. He solidifies carbonic acid; freezes water at the tropics, and even in red-hot crucibles in the Temperate Zone. He also modifies and changes the development of vegetable life, obliterating thorns and spines, altering the color and size of flowers, and the flavor and nutritive character of fruits. And, finally, he has wrought marvelous changes in the form, size, habits, and instincts of the animal creation.[480] Thus in numberless ways does man control, modify, and subordinate nature to accomplish the purposes of his intelligence; but we can not see with Dr. Tyndall how this renders scientific "conclusions founded on the assumed permanence of natural law unworthy of confidence." There is a vacillation in Dr. Tyndall's treatment of this aspect of the subject which renders it difficult to fix his exact position. Does he intend to assert that "personal volition" can not in the slightest degree change the succession of phenomena? Will he say that man does not, and that God can not control and modify and subordinate natural forces so as to bring about _new_ and _special_ results? Unless he is prepared to assert this in the most unequivocal manner, the whole superstructure of his argument falls to the ground. If it is granted that human volition can change the procession of phenomena, and "alter within certain limits the current of events," then _à fortiori_ we may conclude that Divine volition may also interfere in the economy of nature to answer prayer. At one time Dr. Tyndall insinuates that "our notion" (that is, the Christian's conception) "of the Power which rules the universe" is a "mere fanciful or ignorant enlargement of human power,... a _mythologic imagination_ which pictures a being able and willing to do any and every conceivable thing."[481] At another time he admits that "the theory that the system of nature is under the control of a Being who changes phenomena in compliance with the prayers of men is, in my opinion, a perfectly legitimate one.... It is a matter of experience that an earthly father, who is at the same time both wise and tender, listens to the requests of his children, and if they do not ask amiss, takes pleasure in granting their requests.