read the type on page 51 easily and fluently at a distance of ten or twelve inches. If too strong, the print must be brought nearer than ten inches to see clearly, and this will tire the muscles of convergence that turn the eyes inward. If too weak, the fine print will have to be held farther than twelve inches away, and the letters are too small to be seen easily much beyond this distance from the eyes.

The following table gives an idea of about the strength of glasses needed at different ages; but it cannot be strictly followed, as an existing nearsight or over-sight with an old sight will require weaker or stronger glasses than those indicated in the table. The numbers are given in metres as well as inches, as the metric system is now being used by oculists in prescribing, and by most manufacturers of lenses for spectacles.

WHEN TO BEGIN WEARING GLASSES FOR OLD SIGHT.

I have said that old sight is due to loss of accommodative power from hardening of the lens. In youth the lens is quite soft and elastic, but it grows gradually harder, until in old age it becomes as hard as wax. Old sight is therefore not a sudden affection, but one which, advancing gradually, is not noticed until it interferes with our work, and then we resort, or should resort, to glasses.

The putting on of suitable glasses should not be neglected after the early evening symptoms of old sight are noticed. Nothing is gained by waiting, and much may be lost. We lose, in the first place, a great deal of amusement and instruction from the necessity of giving up our evening reading, avoiding small print, resting our eyes, and neglecting fine work of all kinds. In the beginning, these interruptions in our ways of life are not so serious and frequent as to give much annoyance, but as old sight increases they become of importance. In the second place, and of greater moment, is the risk we run of fatiguing and straining the accommodative power of the eyes, and so causing weak sight.

OLD SIGHT DOES NOT MEAN OLD AGE.

In these days of weak sight and eye-glasses

there need be no fear that the adoption of glasses will be interpreted as a confession of old age. Old sight comes very early-much earlier than fortyin most over-sighted eyes, and this flat formation of the eye is more common than any other. I have had to prescribe, now and then, glasses for youth as strong as those usually worn by people sixty and seventy years old. Frequently, even in the best-formed eyes, ill-health, nervous debility, or a constant and severe use of the vision in fine work or night work, will develop the symptoms of old sight as early as the age of twenty-five or thirty. All things being equal, a farmer, if he is not studious, may postpone the use of glasses longer than a professional or literary person, or anyone who reads a great deal. Nothing, however, is gained by postponement: the eyes are not made stronger, and are likely to be made weaker. But if we take the age of forty or forty-five as the average age for the beginning of old sight, it can by no means be considered as the beginning of old age and the intellectual decline that marks its reign. Most men and women do the serious and best work of their lives after the age of forty, and some even after the age of sixty.

Very rapid growth of old sight, requiring a frequent change to stronger and stronger glasses at short intervals, indicates the beginning of a serious

disease of the eye, incident to middle and old age, called Glaucoma.

PECULIAR SIGHT (ASTIGMATISM).

This visual defect may be recognized by looking at vertical and horizontal lines, and comparing their blackness and distinctness at different distances. The letters N and Z on the frontispiece are made up of horizontal and vertical lines. If at any distance from ten to twenty feet one letter appears less clear than the other, there is an inability of the eye to see vertical and horizontal lines equally well. The larger lines may be tried in the same way at from twenty to forty feet. A more complete test than either is perhaps a diagram with lines radiating from the centre like the spokes of a wheel. If any of the spokes appear indistinct or wanting (all being drawn of equal size and blackness), there is defective sight. This defect is, of course, a great hindrance to clear and easy vision in reading, as letters are made up of lines running in different directions.

CAUSE AND CURE OF PECULIAR SIGHT.

This curious defect is due, generally, to a want of symmetry-that is, a want of smoothness, evenness, or roundness of form-in the convex front of the eye-ball. Usually it dates from birth, although

it may not be troublesome enough to attract attention until the eyes are put to considerable use in study, reading, or like occupations.

The cure is in the scientific adaptation of spectacles, or glasses, that neutralize the effect of the imperfect shape of the convex front of the eye. The glasses are peculiarly ground to fit the individual case; and it is perhaps needless to add that the common convex and concave glasses can be of no important help. Indeed, one may always suspect this kind of sight when informed that "no glasses seem to fit," or to give the desired clearness of vision. A good oculist should be consulted, who will see that glasses are properly ground and fitted. The relief to the eyes in reading and sewing which follows properly fitting glasses is very remarkable. A patient of mine had for years suffered from weak sight, weak eyes, inflamed eye-lids, headache, and depression, and had tried all kinds of relief but the right kind. Properly fitting glasses gave her good sight; and as a consequence of this her other ills were banished.

IMMUNITY FROM WEAK SIGHT.

It is probably understood by the reader, from what has been said, that weak sight is very often due to defective form of the eye-ball. It is too flat, too full, or of irregular form. This makes