The natural history of the waters is usually termed Hydrography, or the science which explains the pheno mena, Hydt °statics or Hydrodynamics. In the investi gation of this subject, it is necessary to trace the circu lation of vt ater throughout the globe from the springs at which it issues, and the rivers and lakes through W hich it flows, till it reaches its destination in the great basin of the ocean.
The springs, in reference to the nature of the water, are either nearly pure, or so much contaminated by va rious substances held in solution, as to obtain the deno mination of mineral waters. The temperature of springs deserve attention, as being, in general, similar to the mean temperature of the arr of the district in which they are situated. The situation and duration of springs claim the notice of the agriculturist, as indicating thc rules to be observed in the practice of draining.
The natural history of rivers includes the character of their waters, their channel, and the features of the banks, the length of their course, and the obstacles which they overcome, and the materials which they transport. A knowledge of these circumstances suggests the proper methods to be pursued in embanking rivers and clearing or deepening their channel. It likewise points out to us the origin of many of the appearances whiclt the earth's surface presents, and thus furnishes a solution of some of the most difficult problems in geology.
The history of lakes is still involved in great obscurity. Concerning the origin of these beds, nothing satisfactory has hitherto been advanced. The methods, however, employed by nature to fill them up, and to produce layers of peat and marl, have been studied with care, and useful inferences drawn from them by the agriculturist and geo logist. The knowledge of the depth and temperature of lakes would enable us to stock them with suitable plants and fish, and thus convert extensive sheets of watery wastes into store•houses of food. How much rcmains to be done in this department of rural economy in Great Britain and Ireland ? The Ocean, that great reservoir of the waters of the globe, exhibits, to the historian of nature, ample materials for the employment of his powers of observation and de scription. The field indeed is immense. The motions of the sea, its depth, temperature, and saltness, are all calculated to provoke inquiry, nor are those efforts less meritorious, which are made for the purpose of deter mining the changes which have taken place in its level, its destructive influence on its coasts, and the origin of the sand we observe accumulated on its shores. The
inequalities of the bed of the ocean, though eagerly in quired after by the mariner, have heen but imperfectly explored, as the plumb line is the only instrument which can be employed in surveying them.
The history of the earth, in so far as the naturalist is concerned, is usually termed MINERALOGY. The first object of this science is, to determine the characters of the different substances of which the cr ust of the earth is composed, with the view of bestowing upon them appro priate names, and giving them an accurate classification. Many of these substances exhibit regular geometrical forms, which have been examined with considerable care, and the results now constitute the science of CRYSTAL LOGRAPHY. The naturalist ought next to proceed ill the examination of the manner in which mineral species are associated, the relations which they exhibit to one ano ther, and the beds or strata which result from their union. These beds or strata exhibit determinate relations, in the order of their superposition, in their extent and inclina tion—in their imbedded minerals and organic remains. -These last arc generally termed petrifactions, and the peculiar characters of their condition have made us ac quainted with those vast revolutions, which have con vulsed this globe, disturbed its solid beds, and entombed myriads of plants and animals, which flourished prior to any hutnan ecord, which have left no descendants, ancl no monument to record the nature of the catastrophe which completed their extinction.
There are other circumstances connected with the natural history of the earth, which likewise merit atten tive consideration. It is exceedingly irregular in ap pearance, rising into lofty mountains, stretching out into extended plains, or intersected by valleys and ravines. A variety of causes are operating at present in increas ing or diminishing the inequalities. A careful exami nation of these, is the only method of arriving at a know. ledge of the circumstances which originally were in operation.