culative told us in that experiment, where he says That every degree of obliquity which he gave to the black surface of the canister produced a corresponding effect upou the thermometer? But Dr. Speculative being still determined to resist the voice of Truth, and being still determined to maintain his own speculative opinion; impudently says, "We

1

may therefore conclude in general, that the "remote action of a heated surface is equivalent "to that of its orthographic projection, or can "be estimsted by the visual magnitude of its "source." Our good friend Truth, still true to his trust, resolutely pursues him through all the intricate mazes which he had invented to deceive him, and overturns this sophistical conclusion by the observation which he immediately subjoins to it. He says, "Hence a canister of a "prismatic form, and having its acute angle "turned towards the reflector, will produce the "same impression upon the focal ball, as if, " with an inverted position, it presented its base. This is saying expressly, that the obliquity of the sides of the prism causes no diminution of the effect upon the thermometor; and that it is equally as powerful as when the plain surface of the canister is placed parallel to the reflector. Is not this directly confirming what he told us

he

in his preface to the last experiment, where: says That the obliquity of the canister produced. no sensible difference in the effect? and is it not as positively contradicting what Dr. Speculative told us in that experiment where he That every degree of obliquity produced a corresponding effect upon the thermometer?

says,

It was before observed, that the two succeed¬ ing experiments are mere repetions of the 20th. In the 23d experiment, however, he takes some slight notice of the effect of the clear surface of the canister, when it is brought into action by turning round the canister, along with the black one. But this, he says, proceeds from aberration. And he proposes to correct the error occasioned by this aberration by mathematical calculation. This we have already done in our observations upon the 20th experiment, and there shown the simple fact. But why make use of a canister of this description, which renders calculation necessary to find out the true result? Is it possible to conceive that Dr. Speculative could have any other motive for doing so, but that of involving a simple truth in mystery ; that he might be thereby enabled to mislead our un derstandings. Being seemingly conscious that he was unable to blind the piercing eyes of

Truth by his juggling experiments, Dr. Speculative now fairly flies off into the clouds of speculative mathematical darkness.

"And with him fled the shades of night..

I do not know how Mr. Leslie will relish this catalogue of contradictions which I have mustered up against him. He must have a very extraordinary share of confidence indeed, if he can read them without blushing. He cannot surely be surprised, if the world in general should be disposed to believe, that the portrait which he himself has drawn of the author of these experiments, is a true likeness of his own character.

This mixture of truth and falsehood, which is so conspicuous in Mr. Leslie's description of the different experiments that have come under our observation, is surely a striking example of that perversion of the natural use of language, and consequently of that false construction of it, which prevails so much in the world at this time; and which so particularly characterises the writings of those speculative pretenders to wisdom, who are perpetually obtruding their speculative opinions on the world as established truths. It is, however, only a small but true sample of the whole composition of this .bock,