But the mention of Beachy Head introduces us to another class of lights, known as "coasting" lights, since they are intended to lead the mariner on from point to point along a coast. It will be seen at once that in many cases they do not need to be visible at such great distances as the making lights. When the mariner has sighted the Lizard, for example, he knows where he is. In order that he may learn that important fact as soon as possible it is desirable that that light should have the greatest possible range, but having thus located himself, when he begins to feel his way along the English Channel he is guided by the coasting lights, and so long as they are of such range that he will never be out of sight of one or two of them that will be sufficient. Thus the Beachy Head light, in its present low position, has a sufficient range for its purpose, with the added advantage of more freedom from obscuration by fog. Thus we see how the local conditions and the purpose of each particular light have to be taken into consideration in determining its position and power. The Eddystone, again, is an example of a further class. It simply serves to denote the position of a group of dangerous rocks. Its function is not so much guidance, although no doubt it often serves for that, but for warning. The Lizard light beckons the on-coming ship to the safety of the English Channel; the Eddystone warns it away from danger. The latter, therefore, and similar lights are "warning" lights. [Illustration: _By permission of Messrs. J. and E. Hall, Ltd._ A COLD STORE Interior of a cold store, in which meat and poultry are kept good and fresh by the use of machine-made cold.--_See_ p. 67] Right at the entrance to the English Channel, that greatest of all highways for shipping, there lie the Scilly Isles. This group comprises some few islands of fair size from which we draw those plentiful supplies of beautiful spring flowers, but it also includes a large number of rocky islets which have sent many a strong ship to its doom. On one of the islets, therefore, the Bishop's Rock, there now stands a very powerful light which exemplifies many whose purpose is the double one of welcoming the mariner as he approaches our shores and at the same time warning him of a local danger. Such are both making and warning lights. Of no less importance, though less impressive, are the guiding lights, which guide the ships into and out of harbours and through narrow channels. These are generally arranged in pairs, one of the pair being a little way behind and above the other. Thus when the sailor sees them both, one exactly over the other, he knows he is on the right course.