HARVEY and our HUNTER, effected a revolution in the science of medicine, and led on alone by the independence of his genius, attacked the most prevailing prejudices, so highly provoked the malignant emulation of his rivals, that a conspiracy was raised against the father of our modern practice to banish him out of the college, as "guilty of medical heresy." JOHN HUNTER was a great discoverer in his own science; but one who well knew him has told us, that few of his contemporaries perceived the ultimate object of his pursuits; and his strong and solitary genius laboured to perfect his designs without the solace of sympathy, without one cheering approbation. "We bees do not provide honey for ourselves," exclaimed VAN HELMONT, when worn out by the toils of chemistry, and still contemplating, amidst tribulation and persecution, and approaching death, his "Tree of Life," which he imagined he had discovered in the cedar. But with a sublime melancholy his spirit breaks out; "My mind breathes some unheard-of thing within; though I, as unprofitable for this life, shall be buried!" Such were the mighty but indistinct anticipations of this visionary inventor, the father of modern chemistry! I cannot quit this short record of the fates of the inventors in science, without adverting to another cause of that irritability of genius which is so closely connected with their pursuits. If we look into the history of theories, we shall be surprised at the vast number which have "not left a rack behind." And do we suppose that the inventors themselves were not at times alarmed by secret doubts of their soundness and stability? They felt, too often for their repose, that the noble architecture which they had raised might be built on moveable sands, and be found only in the dust of libraries; a cloudy day, or a fit of indigestion, would deprive an inventor of his theory all at once; and as one of them said, "after dinner, all that I have written in the morning appears to me dark, incongruous, nonsensical." At such moments we should find this man of genius in no pleasant mood. The true cause of this nervous state cannot, nay, must not, be confided to the world: the honour of his darling theory will always be dearer to his pride than the confession of even slight doubts which may shake its truth. It is a curious fact which we have but recently discovered, that ROUSSEAU was disturbed by a terror he experienced, and which we well know was not unfounded, that his theories of education were false and absurd. He could not endure to read a page in his own "Emile"[A] without disgust after the work had been published! He acknowledged that there were more suffrages against his notions than for them. "I am not displeased," says he, "with myself on the style and eloquence, but I still dread that my writings are good for nothing at the bottom, and that all my theories are full of extravagance." [_Je crains toujours que je peche par le fond, et que tous mes systemes ne sont que