It will be interesting to quote for the information of such men, the opinion of the greatest of medieval scientists with regard to the reason why men do not obtain real knowledge more rapidly than would seem ought to be the case, from the amount of work which they have devoted to obtaining it. Roger Bacon, summing up for Pope Clement the body of doctrine that he was teaching at the University of Oxford in the Thirteenth Century, starts out with the principle that there are four grounds of human ignorance. "These are first, trust in inadequate authority; second, the force of custom which leads men to accept too unquestioningly what has been accepted before their time; third, the placing of confidence in the opinion of the inexperienced; and fourth, the hiding of one's own ignorance with the parade of a superficial wisdom." Surely no one will ever be able to improve on these four grounds for human ignorance, and they continue to be as [{42}] important in the twentieth century as they were in the Thirteenth. They could only have emanated from an eminently practical mind, accustomed to test by observation and by careful searching of authorities, every proposition that came to him. Professor Henry Morley, Professor of English Literature at University College, London, says of these grounds for ignorance of Roger Bacon, in his English Writers, Volume III, page 321: "No part of that ground has yet been cut away from beneath the feet of students, although six centuries ago the Oxford friar clearly pointed out its character. We still make sheep walks of second, third, and fourth and fiftieth-hand references to authority; still we are the slaves of habit; still we are found following too frequently the untaught crowd; still we flinch from the righteous and wholesome phrase, 'I do not know'; and acquiesce actively in the opinion of others that we know what we appear to know. Substitute honest research, original and independent thought, strict truth in the comparison of only what we really know with what is really known by others, and the strong redoubt of ignorance has fallen."
The number of things which Roger Bacon succeeded in discovering by the application of the principle of testing everything by personal observation, is almost incredible to a modern student of science and of education who has known nothing before of the progress in science made by this wonderful man. He has been sometimes declared to be the discoverer of gunpowder, but this is a mistake since it was known many years before by the Arabs and by them introduced into Europe. He did study explosives very deeply, however, and besides learning many things about them realized how much might be accomplished by their use in the after-time. He declares in his Opus Magnum: "That one may cause to burst forth from bronze, thunderbolts more formidable than those produced by nature. A small quantity of prepared matter occasions a terrible explosion accompanied by a brilliant light. One may multiply this phenomenon so far as to destroy a city or an army." Considering how little was known about gunpowder at this time, this was of itself a marvelous anticipation of what might be accomplished by it.
RATHHAUS (TANGERMÜNDE)
Bacon prophesied, however, much more than merely [{43}] destructive effects from the use of high explosives, and indeed it is almost amusing to see how closely he anticipated some of the most modern usages of high explosives for motor purposes. He seems to have concluded that some time the apparently uncontrollable forces of explosion would come under the control of man and be harnessed by him for his own purposes. He realized that one of the great applications of such a force would be for transportation. Accordingly he said: "Art can construct instruments of navigation such that the largest vessels governed by a single man will traverse rivers and seas more rapidly than if they were filled with oarsmen. One may also make carriages which without the aid of any animal will run with remarkable swiftness." [Footnote 5] When we recall that the very latest thing in transportation are motor-boats and automobiles driven by gasoline, a high explosive, Roger Bacon's prophesy becomes one of these weird anticipations of human progress which seem almost more than human.
[Footnote 5: These quotations are taken from Ozanam's Dante and Catholic Philosophy, published by the Cathedral Library Association, New York, 1897. ]
It was not with regard to explosives alone, however, that Roger Bacon was to make great advances and still more marvelous anticipations in physical science. He was not, as is sometimes claimed for him, either the inventor of the telescope or of the theory of lenses. He did more, however, than perhaps anyone else to make the principles of lenses clear and to establish them on a mathematical basis. His traditional connection with the telescope can probably be traced to the fact that he was very much interested in astronomy and the relations of the heavens to the earth. He pointed out very clearly the errors which had crept into the Julian calendar, calculated exactly how much of a correction was needed in order to restore the year to its proper place, and suggested the method by which future errors of this kind could be avoided. His ideas were too far beyond his century to be applied in a practical way, but they were not to be without their effect and it is said that they formed the basis of the subsequent correction of the calendar in the time of Pope Gregory XIII three centuries later.
It is rather surprising to find how much besides the theory of lenses Friar Bacon had succeeded in finding out in the department of optics. He taught, for instance, the principle of the aberration of light, and, still more marvelous to consider, taught that light did not travel instantaneously but had a definite rate of motion, though this was extremely rapid. It is rather difficult to understand how he reached this conclusion since light travels so fast that as far as regards any observation that can be made upon earth, the diffusion is practically instantaneous. It was not for over three centuries later that Römer, the German astronomer, demonstrated the motion of light and its rate, by his observations upon the moons of Jupiter at different phases of the earth's orbit, which showed that the light of these moons took a definite and quite appreciable time to reach the earth after their eclipse by the planet was over.