and so troublesome, when a sufficient degree of ablution has not been observed; and which, if suffered to continue, may become, perhaps, both difficult of cure, and dangerous in its consequences. The remedy is to be found in cleanliness, repeated washing, and, if necessary, some slightly stimulating lotion to relieve the enfeebled vessels, and strengthen the skin of the part.

In the efforts to cultivate this sense, it is desirable to teach children to distinguish at first simple sounds, and by degrees those which are more complicated, or at least compounded of several simple tones; together with their relative distances, and the precise spot whence they come. It is extraordinary, but not more so than true, how little we possess naturally the means of distinguishing the direction in which sounds approach us. Every one whose opportunities have permitted the experiment, must have remarked, that if he endeavoured during the night to form an opinion, upon which way a stage coach passing his window was travelling, he has been frequently deceived, and oftener wrong than right. Habit, and the want of exercise, render it difficult to distinguish these slighter differences; but education may supply the deficiency, and give a greater degree of accuracy to the monitions of this sense and it is self-evident, of how great importance such an acquisition may be to the individual and his conservation.

In the further improvement of hearing, it is

desirable to teach children to recognize persons and things by certain appropriate sounds; to become acquainted with the footsteps of individuals, the different cries of animals, and indeed every variety of sonorous vibration, in order to give a greater degree of accuracy and energy to the organic impressions. In effecting these objects, the first thing to be taught, is the faculty of attention; the direction of the organ towards the purpose of obtaining every possible notice. Having secured the attention, (no contemptible conquest in the volatile age of childhood,) the parent will proceed to develop the power of hearing quickly, as well as accurately; and of keeping up the effort of listening without fatigue, as well as of discriminating the slighter shades of articulate sounds, and their minuter variations.

There are a number of methods, through which the exercise of this sense may be carried on by means of the impression of natural objects upon it; such are the tones of the human voice, the varied expression of feeling, and the conventional result of articulate language. Nor is this unimportant; for through the medium of the ear, our sympathy with others is extensively awakened; and in addition to our widening sphere of intelligence, through the aid of language, which will again come to be considered in a subsequent chapter, we are also roused to a sense of feeling. The accents of joy, the shriek of sorrow, the cheering of courage, the soft breathings of love, the con

solations of pity, &c. all awaken corresponding emotions, and enrich the understanding with a thousand ideas, arising out of the social state, and connected with all our best hopes, and views and feelings, and actions; while they powerfully aid, and gently stimulate the imagination. The latter property should be carefully watched with those, whose too luxuriant fancy is a little liable to run wild; and especially should they be guarded from the excessive influence of music. Its soft luxury should only be sparingly permitted to children of fervid sensibility; while their imaginative musings, fostered by the harmony of sound and song, should be counteracted by giving a preponderating largeness and weight to the understanding.

We shall only farther remark, that the sense of hearing is liable to be powerfully affected by any cause of morbid irritation to the brain and nervous system, to the energy and well being of which, the prosperity of this sense must be for ever indebted it is therefore necessary to be watchful against the imprudent stimulation of that organ and its appendages.

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CHAP. XV.

EXERCISE OF THE SENSES CONTINUED

OF THE SENSE OF SIGHT-ITS OBJECT-RAYS OF LIGHT THEIR DIFFERENT CAPACITY FOR CALORIC-LAWS REGULATING THEIR TRANSMISSION-THE EYE IS THE ORGAN OF SIGHT SKETCH OF ITS PHYSIOLOGY— DIFFERENT DEGREES OF VISION, AND THE POWER OF ACCOMMODATION OF THE EYE TO VARYING CIRCUMSTANCES-SIGHT IS ACTIVE OR PASSIVE, VOLUNTARY OR INVOLUNTARY-ITS USES-ITS HIGHEST STATE OF PERFECTNESS-IMPROVED BY CULTURE AND ASSISTED BY THE OTHER SENSESOPTICAL ILLUSIONS -POWER OF EDUCATION, HABIT, AND EXERCISE-DEFECTS IN VISION-DISTINCT VISION HOW PRESERVED-PRECAUTIONS ON THIS SUBJECT-THE CORRECTION OF BAD HABITS-THE MODIFICATIONS OF EXERCISE-TOGETHER WITH THE DIRECT AND INDIRECT ADVANTAGES RESULTING FROM THEM-INTELLECTUAL AND MORAL ASSOCIA

TIONS, &c.--DEFORMITIES OF VISION—SQUINTING –

METHOD OF CURE-CONCLUSION.

V. Of the Sense of Sight.

THE immediate object of this sense is that which imparts the idea of colour; and this is dependent upon the rays of light reflected from different bodies, and passing directly or indirectly to the sentient organ, in separate pencils, with a dis

tinctness which baffles confusion; and with a velocity so great, as at short distances to be quite inappreciable. Thus a body reflecting all the rays of light, appears white; red, where it has the power of reflecting only the red rays, and so with regard to all the primitive colours, and the shades which are compounded of their union; while black, or the absence of all colour, results from the absorption of the entire light.

These rays possess a different capacity for caloric, the maximum of which exists in the red ray; so that substances will not only give the sensation of warmth according to the inverse ratio of their power of reflecting, or the direct ratio of their power of radiating or transmitting the rays of light; but also according to their power of reflecting or transmitting particular rays: a circumstance worthy of attention in selecting the dress of children, as it may not only contribute to their comfort, but as it may avoid also the too great irritation of an important and highly delicate

organ.

The rays of light are also partly dependent upon the medium through which they pass: thus they may be reflected from some bodies, according to laws, which admit of being ascertained or defined; and yet pass in right lines so long as they continue in the same medium: but in passing from a rarer to a denser medium, or from a denser to that which is more rare, they are bent from their straight course, and acquire a