ham Harbour. 3rd, because the experience we have as to working iron, brick, and wood, renders it certain that we may construct a cylinder, (pipe, tube, or tunnel-call it what you please) of that length, large enough for persons and goods to be conveyed through; and effective as to the purpose contemplated, of either of these materials; and I here pledge myself to bring forward parties willing to contract for its execution and guarantee that it shall be tight and efficient for the purpose, whenever necessary. 4th, because the effect of the practical illustration of the principle which I have in operation, proves that we can make the atmosphere move a carriage capable of conveying both persons and goods, by actually doing it; as many persons have witnessed and experienced. 5th, because this illustration of the principle is practical, excepting that instead of being so long as would be necessary to serve as a mean of conveyance between Brighton and Shoreham Harbour, it is only of such a length as my humble

1 The main pipe which conveys gas from the works at Hove to the eastern extremity of Brighton, is above three and a-half miles long. And the length of that of the West Bromwich and Biriningham gas works is stated to be nearly seven miles. The length of the whole of the pipes of the Hove gas works is 16 miles.

means admitted of my extending it to-i. e. 150 feet. In size, however, it is fully practical, being nearly eight feet in diameter; and the air pumps are capable of exhausting all the air out of a tube of that size, extending from Brighton to Shoreham Harbour, in half an hour. 6th, because common sense informs us, that if it be possible to put the principle into operation, on a scale which is similar to what I propose as to Brighton and Shoreham, excepting that it is not so long, it must be equally possible to extend it that distance as it is to lay down pipes, and send water or gas through them so far. And lastly, because it is impossible that the money expended in doing this, can ever be lost: as even were the plan of transmission I propose by atmospheric pressure utterly to fail, still would the tunnel serve for, and be efficient as a railway, on which either horses or loco-motive engines would draw more than the same power could draw on any other railway.

These are the reasons which induced me to make the proposition I have publicly submitted. Without even adverting to, much less refuting them, you have cast contempt on the proposition by mis-stating it: it therefore became necessary for me to rectify the abuse; and having done so, I proceed to enquire in

what proportion your accuracy as a critic, surpasses your justice as a disputant.

Criticism is, I believe, generally understood to mean, an examination into the merits of a question; and I apprehend, universally received as an assumption on the part of the critic, to be competent to examine, and pronounce upon the question he criticises. It is expected of him that he shall have fully informed himself upon those particulars which bear on the subject of his scrutiny; and that his decision shall not be impugnable on the grounds of ignorance with respect to points essential to the correct apprehension of the proposition.

With these views of the duties and powers of those who take on themselves the dignity of dispensing judgment from the imperial chair of criticism, it was with no small surprise, I found, on submitting myself to the ordeal, that in his eagerness to condemn, the Minos before whom I stood, had neglected to examine; and that I should in consequence have to appeal from his decision, on the grounds of incompetence to decide justly, from sheer ignorance as to those points on which depends the very power of comprehension. Yet such is the case; and I accordingly do appeal from the judgment you have pro

nounced, as ungenerous in reference to the individual, and unjust as relates to the merits of the case. I support this appeal as follows. First, because you do not even comprehend the nature of my proposition. Had you taken the trouble to examine before you condemned, you would have learned that your observation, "besides which no human being could exist in air so highly rarified as that would require to be to move at all," has no application whatever to the case; since the persons who might be conveyed by the method I propose, would not be exposed to, nor obliged to respire air at all rarified. My words are

"Nor are the objections we at first conceive, relative to the effect which pumping air from the cylinder, and producing what only the word vacuum (inapplicable as it will by and bye be seen) will enable us to convey the idea of, at all more tenable. The degree to which air would be exhausted from the cylinder, might scarcely ever be sufficient to sink a barometer two inches lower than one exposed to the atmosphere stood at; so that even were we exposed to it, no inconvenience would be felt. But we never shall be exposed to it, any more than those who witness the cruel experiment of putting a mouse under the receiver of an air pump and then exhaust

ing it, are exposed to what the little animal suffers. Between those who see, and the poor creature which feels the effect of the apparatus, is the side of the receiver. And between the part of the cylinder in which the exhaustion, or rather the difference of density is, and the passengers in the vehicle, would be the end of the vehicle; so that though close to them would be an atmosphere rarer than (we will suppose) it might prove pleasant to be in, yet would the atmosphere they actually were in, be the same as that of the air at large."1

Now, with the theory stated explicitly as is here done, and with my practical illustration, proving the truth of it, your observation, "that no being could exist in air so highly rarified, &c. &c.," shews incontrovertibly that you have held up to public contempt and reprobation, what you do not even comprehend; and is an irrefutable proof, that in replying "most certainly," when at the Public Meeting you "put it to me as a scientific man, whether your experiencing the operation of the principle would have enabled you to form a better judgment of the plan or not," I was quite right.

1 Air of only three-fourths, two-thirds, half, and in Joliffe and Cornillot's ascent, of less than half the usual density (the barometer sinking to 12. 15), has frequently been respired, without any serious consequences.