But whatever the comparative amount of influence of the gun and the printing press, there can be no doubt that they have worked together hand in hand: that one guarded, and the other assisted, the first tottering steps of the Renaissance movement, and that both have continued to guard and assist the grand march that soon began, and that is still advancing.
As the circumstances surrounding the invention of both the gun and the art of printing are sufficiently well known to warrant the belief that each was made, not by a king or any other man of high position, but by a man relatively obscure, and that the surroundings and early life of both were not those of courts or palaces, but those of a humble kind, it may be well to note how enormous are the results that have flowed from causes that seem to be very small. We have been told that "great oaks from little acorns grow"; but the consequences that have grown from the conception of the idea of printing are larger than any oak; and an acorn is probably much larger than the part of the brain in which an idea is conceived.
As a matter of interest, let us realize the strong resemblance between the impression we receive from a material object actually seen by the eye and the memory of that impression afterwards. Let us then realize the strong resemblance between it and another impression of that same object seen mentally but not physically; for instance, let us realize the strong resemblance between the impression made on us by actually seeing some friend and the impression received by _imagining_ him receiving a letter which we are now writing to him. The first picture was an image of the external object that was physically made on the retina, as a picture or image is made by a camera on a screen; but that picture on the retina must have been seen by the brain, or we would not have known of it. The other pictures were not made physically on the retina, so far as we know. Yet we all realize that we can make pictures on our minds the more readily if we close our eyes. The fact of our eyes being open seems to operate adversely to our receiving a clear mental picture.
Now it is a matter of fact that an object (for instance, a pole) can be seen by a person with normal eyesight, if it subtends an angle as great as one minute; that a pole a foot thick can be seen clearly from a distance of 3600 feet, at which distance it subtends that angle. The rays of light pass through the crystalline lens of the eye and are focussed on the retina, as they pass through the lens of the camera, and are focussed on the sensitized paper. Assuming the distance from the crystalline lens to the retina to be about three-quarters of an inch, the pole would be represented on the retina by an image 3/(4 x 3600) or less than 1/4000 of an inch wide. During daylight our retinas are continually receiving images of which all lines as wide as 1/4000 of an inch (and much narrower) are very clearly apprehended by the mind.