Among the latter kind of secrets are the lives and habits of the creatures of the deep, and the causes and effects of those singular currents of air and water, which, to the eye of ignorance, seem to be nothing better than irregularity and confusion; but which, to the minds of those who search them out, and have pleasure therein, are recognised as a part of that wonderful, orderly, and systematic arrangement of things that we call Nature: much of which we now know, more of which we shall certainly know, as each day and year adds its quota to the sum of human knowledge; but a great deal of which will, doubtless, remain for ever hidden in the mind of nature's God, whose ways are wonderful, and past finding out. It is the latter class of secrets to which we purpose directing the readers attention in the following pages. On approaching so vast a subject, we feel like the traveller who, finding himself suddenly transported into the midst of a new and magnificent region, stands undecided whither to direct his steps in the endlessly varied scene. Or, still more, like the visitor to our great International Exhibition of _1862_, who,--entering abruptly that gigantic palace, where were represented the talent, the ingenuity, time wealth, and industry of every people and clime,--attempts, in vain, to systematise his explorations, or to fix his attention. It is probable that, in each of these supposed cases, the traveller and visitor, resigning the desire to achieve what is impossible, would give themselves up to the agreeable guidance of a wandering and wayward fancy. Let us, reader, act in a somewhat similar manner. Let us touch here, and there, and everywhere, on the wonders of the sea, and listen to such notes of the Ocean's Voice as strike upon our ears most pleasantly. CHAPTER TWO. COMPOSITION OF THE SEA--ITS SALTS--POWER AND USES OF WATER--ADVANTAGE AND DISADVANTAGE OF SALTS--ANECDOTE--DEEP-SEA SOUNDINGS--BROOKES APPARATUS--IMPORTANCE OF THE SEARCH AFTER TRUTH--ILLUSTRATIONS-- DISCOVERIES RESULTING FROM DEEP-SEA SOUNDINGS. Before proceeding to the consideration of the wonders connected with and contained in the sea, we shall treat of the composition of the sea itself and of its extent, depth, and bottom. What is the sea made of? Salt water, is the ready reply that rises naturally to every lip. But to this we add the question,--What is salt water? or, as there are many kinds of salt water, of what sort of salt water does the sea consist? To these queries we give the following reply, which, we doubt not, will rather surprise some of our readers. Fresh water, as most people are aware, is composed of two gases--oxygen and hydrogen. Sea water is composed of the same gases, with the addition of muriate of soda, magnesia, iron, lime, sulphur, copper, silex, potash, chlorine, iodine, bromine, ammonia, and silver. What a dose! Let bathers think of it next time they swallow a gulp of sea water.