suggestive, encouraging, and recording one or two more attempts in the right direction, amid much sad gaping of crowds at men and ponies swinging from big bladders.

So the subject was to be got up,' beginning of course at the latter end, and working backwards-as is good in matters of History. Very few books were to be found treating the subject at all; the encyclopædias not generally very communicative on the matter; but a few pamphlets to be dug out of bookstalls, a specification or two in the patent records, a considerable number of papers in journals English and French, not much in other tongues. All this was to be waded through, to discover why we are still travelling by sea, and not by the ocean that comes up to every man's door.'

Of course I found many of my notions anticipated, sometimes single suggestions inadequate of themselves even to make a step towards success; sometimes complicated with other devices which in practice would frustrate their intention. I met, however, with very few accounts of actual experiments, none, of any, the failure of which could not have been predicted, or of which the insufficiency for more than a very partial result was not obvious. I found but one Englishman of any high scientific attainments who had given much assiduous and hopeful attention to the subject, and who, after having carefully examined all its difficulties and facilities, had given his judgment, that the navigation of the air is a possibility. The conviction of this gentleman, recorded nearly half a century ago, and often repeated since in scientific journals, was thus expressed in a letter to myself: 'I have no doubt whatever that I could at once put together a balloon that should carry its passengers at twenty miles an hour.' If Sir G. Cayley's untiring advocacy of aerial navigation, had ever

been met (when he proposed to form an Aeronautic Society) by any of the enthusiasm which assisted the Montgolfiers and MM. Charles and Robert to work out their project, there would have been no room by this time for such a volume as the present. I should state, however, here, that even Sir G. Cayley's scheme is not quite satisfactory to my mind: from the magnitude on which alone it was supposed by him to be practicable, and from an oversight in the proposed adjustments, which on experiment would have been fatal to its success at first, though it would no doubt soon have been remedied.

If this gentleman did not seem to me to have fully solved the problem, or to have stated it so that it could be at once solved on mechanical trial, assuredly no other projector has, so far as I can learn, shown how a true navigation of the air may be effected. It was not till after I had completed my own views of this matter, and had become pretty well acquainted with former schemes, that an experiment was publicly made in Paris by a poor working man, which went further to clear the way through the air than has yet been shown. But it did not go far enough into the matter, and left untouched the vital point -the motive power-the foundation for which most aerial schemers had forgotten to provide, scarcely anyone but Sir G. Cayley has attempted to secure, It seemed then that the field was still open.

But, besides the enquiry as to how the main question stood, it was necessary to ascertain what data were already to be found in our stores of knowledge, from which the amount of difficulty to be overcome, and the means at hand for meeting it, could be at once stated and compared. Very few such data are to be found: absolutely none on the most vital points, except generalities, all promising

a

success.

It is indeed somewhat remarkable that scientific men should have been so long contented, as they have for the most part been, with assuming that aerial propulsion is impossible, not only without making any attempts to demonstrate that it is so, but without trying or even quoting a single experiment at all applicable to the purpose upon the most important condition in the problemviz., the Resistance of the Air.

The result then of my enquiry was, that I could not learn from books that my notions were either ancient or impracticable. But in the absence of exact data, from which the problem might be calculated to precision, experiments were to be made to obtain them and it would have been infinitely more satisfactory to me to have put forth what I have to offer, in the form of numerical results of careful experiment, than to have uttered them as mere suggestions.

The impediments to my wish have been twofold: Firstly, the expenditure of time and money too great for my limited means, yet necessary to the extortion from nature of a full and exact answer as to certain conditions on which accurate details are preferable to general certainties. Secondly, the fact that when I had selected two or three special points for personal examination, I was disappointed in the pursuit of the study by failure in the completion of the apparatus ordered for the purpose, partly by mistakes, partly by delay in the execution. So that after six months passed now in patient waiting, now in exhortation to speed, I have been obliged to content myself with pointing out the lines and modes of enquiry which I consider necessary and sufficient to prepare a fair start for the navigation of the air.

If any person-physicist or engineer-should conde

scend to read these pages, and should conceive that some better apology than this is due to him for venturing into print without new experimental results, and elaborate mathematical form of proof; he must please to take these considerations. Firstly, that myself to try all the experiments which suggest themselves would have been impossible; and that not to try to put others in the way of doing what oneself cannot accomplish, is not the most patriotic plan, and not the one which Bacon followed, though it may be the most scientific. Secondly, that calculations founded upon imperfect data, cannot give numerical results worth anything, though they may be very amusing to those whose talent lies in figures and symbols, and very likely to give an air of profundity to reasoning that may be but shallow; or like the coating of a bubble may have no bottom at all to rest on.

Finally as to the object of my book, I cannot exclaim in legitimate prefatory style, that if I shall have succeeded in awakening in one bosom the love, &c., &c., or in inducing one more competent than myself to take in hand, &c., &c., for the benefit of humanity, my wish will have been fulfilled. I do not entertain either of these wishes very fondly, though I should be very glad of either result, of the latter especially. My object in writing it, will be simply to deliver my brain of a burden which came upon it uninvited, and which will not quit it at my bidding without receiving leave to rush into the press.

CHARLES BLACHFORD MANSFIELD.

March 18, 1851.