290 THE THE ATM EN T OF DISEASES. 



power is required than for day work. When the night spectacles are changed 

 because they are not strong enough, they should be used in the daytime. It is a 

 great thing to get a comfortable pair of spectacles or double eye-glasses ; should 

 there be any doubt about them they should be changed, always, of course, under 

 the direction of the ophthalmic surgeon. Many people use a " reading-glass," from 

 three to five inches in diameter, set in a frame with a handle, and there is no 

 objection to it, although it is far less convenient than a pair of spectacles. Old 

 sight does not of necessity mean old age, for some people suffer from this defect of 

 vision before they are thirty. 



Spectacles and Eye-glasses. We must say a word or two on this subject. The 

 absolute necessity of purchasing the glasses under the direction of a qualified person, 

 and of not going into a shop at random and taking just what the shopman gives 

 you, has already been pointed out. In the mechanical arrangement of the lenses- 

 there are two or three points worthy of attention. The frames should be of metal, 

 and sufficiently strong to prevent twisting or loss of weight. Steel is probably the 

 best, although some people prefer gold. Lightness is, of course, essential to comfort. 

 The nose piece, or saddle, should be carefully adjusted to fit the nose. Their pattern 

 is a matter of taste, though the oval is generally considered to be the most becoming. 

 The lenses themselves may be made of crystal that is, Brazilian quartz or of 

 crown glass. The crystal is harder than glass, and is therefore less likely to scratch r 

 and is not so liable to get broken. Moreover, it takes a higher polish, and being 

 more refractive, it may be made of less thickness than glass. The great difficulty is- 

 to get a piece of crystal free from specks and impurities. Dishonest dealers often 

 supply crown glass for crystal. The best way to distinguish between them is to 

 apply a file to the edge of the material ; glass cuts readily, but crystal is much harder. 

 Crown glass lenses are very good, and may be used when the spectacles have to be 

 changed often, or when expense is an object. Tinted or coloured lenses are some- 

 times used, but only when they are made of glass. As a rule, they are objectionable, 

 because they remove the natural stimulus of white light, and thus make the retina 

 unduly sensitive. 



Eye-shades are sometimes used with advantage, especially when a bright light is 

 objectionable. They may be made of fine fabric, of gauze coloured black, or, what i& 

 still better, plain grey. It is curious that shades are not more largely used as pro- 

 tectors for the eyes by artisans and others employed in work pi-educing chips or 

 fragments. Blue gauze wire set in a spectacle frame would answer the purpose 

 admirably, especially if it were somewhat cup-shaped, so as to guard the eyes at the 

 side. When the particles are not hard or are not driven with force, and especially 

 when accurate light is required, as in lathe-work, thick glass set as spectacles would 

 suffice. For reading, a shape that will protect the eyes from the direct rays of light 

 is useful. 



FAINTIXG. 



A fainting-fit arises from sudden failure of the heart's action. It is met 

 with most frequently in young adults, especially in young females. Its occurrence 

 is favoured by general debility or ill-health, and more particularly by anaemia, or 



