Lieutenant Totten of the United States Army, in writing about explosives and big guns, discusses carefully the question as to the best kind of explosive for actual service; that which will expend its entire force in driving out the projectile. With the large-grained gunpowder now in use about half of the charge is wasted, while gun-cotton and dynamite exert an injurious strain upon the gun. As a way out of the difficulty, he recommends a 'compensating powder,' each grain of which contains a core of gun-cotton, and he points out that forty pounds of this powder would be sixty pounds stronger than a hundred-pound charge of gunpowder. The explanation is that by the time forty pounds of the hundred are burned, the shot has left the gun; consequently, sixty pounds are of no help to the shot. But if the forty pounds contain fifteen pounds of gun-cotton, then this cotton, when fired, acts on the already moving shot under the most favourable circumstances as a pure accelerator, and does not injure the gun. In this way, writes Lieutenant Totten, 'we eliminate the great waste of the one, curb the straining action of both, and obtain a true artillery powder, lighter, and four and a half times more effective, charge for charge, than our best gunpowder.'
An address 'On Light in some of its Relations to Disease,' delivered to the Albany Institute (State of New York) by Dr Stevens, sets forth views and facts which are worth consideration. Light, as we know, is on the whole beneficial; but may there not be cases in which it is harmful when passing through the transparent media of the human eye? Dr Stevens is clearly of opinion that many nervous diseases are aggravated if not produced by defective vision. The strain on the muscles of the eye, when long continued, sets up an irritability which tells injuriously on the nervous system, and neuralgic affections. St Vitus's dance and severe periodical headaches are the consequence. Rectify the imperfection of the sight, says Dr Stevens, by proper spectacles, and the nervous disease will be either mitigated or cured. It is of no use to buy glasses at hazard because they seem to suit the eye; for none but a scientific oculist can really decide, after careful experiment, on what is proper. In many cases the focus of the two eyes is not the same, and each must have its proper glass. Professor Donders of Utrecht was the first to point out that the so-called 'cylindrical glasses' were generally the most efficient; and since then 'the science of correcting anomalous refractions of the eye has been brought to a perfection which is truly wonderful.'