It will be obvious from what is here stated that the attempt to discover an oil-supply in Derbyshire must not be regarded, at present, as more than a praiseworthy and interesting enterprise. There is no room for doubt that the best expert opinion has been brought to bear on the matter. A small quantity of petroleum has already been raised; but whether the flow will be sufficient to cover the expenses of the boring, and how long the flow may last, or how much it may amount to, are matters quite impossible to foretell. In any case, it is in the highest degree improbable that such an abundance of oil will be obtained as to count much, if at all, in the world's production of petroleum. It must also be remembered that products similar to those yielded by petroleum are already extracted in quantity as a remunerative industry by the distillation of oil-shales in various parts of the United Kingdom; and that there are oil-shales in this country still unworked. So that we need not be in despair if we do not tap an oil-spring of any importance close to hand. The world's supply is still open to British enterprise. Another reflection of some importance is that these world-wide sources of rock-oil or petroleum are likely to be exhausted by exploitation much sooner than are the coal-fields of the world. We cannot rely on their long duration. CHAPTER XXII THE STORY OF LIME-JUICE AND SCURVY From mediæval times onward a serious constitutional disease–a morbid condition of the blood and tissues–has been known by the name "scurvy," and the word "scorbutic" has been coined from it. It is to-day practically unknown in the ordinary conditions of civilized life, but formerly was common, and the cause of disablement and of frightful mortality in ships' crews, beleaguered cities, armies on campaign, and war-stricken regions. It begins with a certain failure of strength. Breathlessness, exhaustion, and mental depression follow. The face looks haggard, sallow, and dusky. After some weeks the exhaustion becomes extreme; the gums are livid, ulcerated, and bleeding; the teeth loosen and drop out; purple spots appear on the skin; ulcers break out on the limbs; effusions of blood-stained fluid take place in the great cavities of the body; profound exhaustion and coma follow; and death results from disorganization of the lungs, kidneys, or digestive tract. It was recognized in early times that the disease was dependent on the character of the food of those attacked by it; and not the least of the horrors accompanying it was the terror caused by the well-founded conviction that the appearance of a single case in a ship's crew or other specially circumscribed community was an unfailing index, and meant that all were likely within a few days–owing to the enforced identity of their food and conditions of life–to develop the disease. Often, in past centuries, a half or two-thirds of a ship's company have been carried off by it before a port could be reached and healthy food