acoustics from the same general point of view, and deals with atmospheric wave-motion in connection with the properties and constitution of the various forms of matter. The researches on the formation of clouds in tubes filled with various gases and vapors under the influence of the electric beam, and the resulting inquiry into the subject of atmospheric dust, were but parts of the same comprehensive investigation into molecular conditions and transformations.
Prof. Tyndall has won his scientific reputation as an explorer in the field of experimental physics, but he has also a commanding position as a philosophic thinker. The questions that can be resolved by experiment lead on to questions that can be resolved only by reason. Philosophy is old and easy, and the human mind has overflowed with it from the beginning; but philosophy grounded in the knowledge and method of science is as yet rare, though it is nevertheless a glorious reality. If scientific thinking is the result of an apprenticeship of centuries in the management of the intellect, and if the mind's scientific action is its most perfect action, then must scientific men, as the world goes on, be more and more trusted in their opinions. Such is undoubtedly the present tendency. This is shown generally in the increasing recognition of the scientific school of philosophy, and it is specially exemplified, in the present case, by the interest that is taken in whatever Prof. Tyndall has to say to the public, and whatever the subject on which he speaks. This high scientific position gives acknowledged weight and force to his views. But Prof. Tyndall's philosophic cast of mind not only attracts him to the deeper questions of the time, but his courageous temper leads him to deal with them candidly and fearlessly. First of all, a devotee of science and a lover of truth, he gives to these his sole allegiance. An independent and intrepid inquirer, tolerant of honest error, but contemptuous of that timid and calculating spirit which would protect men's prejudices from the light of investigation, he is without fear in the free and manly expressions of his opinions. That these should often contravene prevailing beliefs is inevitable. A Protestant by hereditary instinct and in his blood, and long drilled in the severities of scientific logic, it is impossible that he should not find much in current opinion to excite continued and trenchant protest.
Allied with this cherished freedom of thought and utterance, there is in Prof. Tyndall's character an intense love of justice, and a passion for fair dealing that is quite chivalric. This temper has been displayed on various occasions, but in none more conspicuously than in his generous defence of the German physicist, Mayer, whose scientific claims he considered to be depreciated by English scientists. Mayer's had been a hard fate. An undoubted pioneer in establishing the important doctrine of the correlation of forces, working out its several lines of proof with marvellous sagacity and an amount of exhausting labor that resulted in mental derangement, and with little sympathetic recognition