EYE-SIGHT, ITS DEFECTS AND TREATMENT. 



271 



Union, namely, first, it has proved to ocular 

 demonstration the immense and varied unde- 

 veloped resources of the South ; and second, by 

 the interchange of ideas, opinions, and courte- 

 sies between intelligent and reflecting men of 

 both sections which it afforded, the men of the 

 North and of the South have learned to esteem 

 each other more, to see the fallacy of the de- 

 preciative representations by unscrupulous pol- 

 iticians on both sides, by which they were 

 respectively misled and estranged, and by dis- 

 sipating the prejudices which made Georgia a 

 terra incognita to the citizen of Massachusetts, 

 and Maine a remote foreign country to the 

 citizen of Georgia, to promote social and com- 

 mercial intercourse between them, and finally 

 exert a good influence in shaping the policy of 

 the Federal Government. 



The financial result of the enterprise may 

 be stated in round numbers as follows: 



Cost of buildings, etc $160,000 



Running expenses 100,000 



Total $260,000 



Subscriptions $120,000 



Entry-fees, gate-receipts, etc 135,000 



Sale of buildings 25,000 



280,000 



Leaving for distribution to stockholders $20,000 



When all the accounts are paid, it is not im- 

 probable that this apparent surplus will be 

 reduced to zero. As none of the stockholders 

 expected any return when they subscribed, and 

 as they contributed with a view only to pro- 

 mote the success of a " World's Fair " at the 

 South, the number of dollars to be returned to 

 them is not a matter of any moment. 



The buildings have been purchased for $25,- 

 000 by a stock company, who have also bought 

 the land from the city of Atlanta for $15,000, 

 with a view to establish immediately a cotton- 

 mill with not less than ten thousand spindles, 

 with capacity of increase to twenty thousand, 

 and with looms sufficient to weave the yarn 

 from all the spindles employed. The name of 

 the factory is to be the "Exposition Cotton 

 Mills." 



EYE-SIGHT, ITS DEFECTS AND TREATMENT. 

 In no branch of practical science has there 

 been greater advance in recent years than in 

 that which pertains to the structure and func- 

 tions of the human eye. Perhaps the most 

 important conclusions lately reached are those 

 which have definitely determined the method 

 by which the vision is adapted to near and 

 remote objects, and have ascertained the best 

 means of preserving this power and of rectify- 

 ing its deficiencies. The similitude of the eye 

 to the camera of the photographer is quite fa- 

 miliar. It is well known that the rays of light 

 proceeding from external objects enter the 

 eye through the cornea or projecting horny 

 substance in front, pass through the pupil, or 

 opening in the iris, into the dark chamber of 

 the eyeball, and are there brought together by 

 means of a lens so as to form an inverted pict- 

 ure of the object on the retina at the back of 



the chamber, which retina is a screen formed by 

 the outspread fibers of the nerve that comes in 

 from the brain. But while there is here a dis- 

 tinct analogy between the eye and the camera 

 obscura, there are differences which are curi- 

 ous and important. In the photographer's in- 

 strument the rays are brought together on a 

 flat surface, and no combination of lenses has 

 yet been contrived to overcome completely the 

 disadvantage of sharply defined details in the 

 center, shading off into indistinctness about 

 the edges of the picture. The maximum angle 

 subtended by the field within which a tolera- 

 bly clear image can be obtained is forty-four 

 degrees, while in the eye, owing to the concave 

 surface on which the rays are received, a field 

 of one hundred and sixty degrees is obtained. 

 The vision is not sharp over all this area, owing 

 to the constitution and distribution of the nerve- 

 fibers of the retina. In fact, the area of clearest 

 sight is very restricted, but the relatively large 

 surrounding surface of inferior sensitiveness 

 serves the purpose of giving notice of the pres- 

 ence of objects in a wide field of vision, and 

 guiding the eye to a closer scrutiny of them by 

 means of its wonderful facility of movement. 

 The optic nerve, which enters the back of the 

 eye from the brain and constitutes the channel 

 of visual impressions, is a white cord nearly 

 one sixth of an inch in diameter, and is com- 

 posed of fine threads, at least 250,000 in num- 

 ber. These spread out to form the retina, 

 which is rather a mosaic pavement than a true 

 net- work. The ends of some of the threads 

 turn back upon themselves and form relatively 

 thick cones of nerve-matter, while others ter- 

 minate abruptly in rod-like ends. These are 

 distributed somewhat irregularly, being close- 

 set only at one central point directly back of 

 the pupil. This is the one spot of supreme sen- 

 sibility, and, being slightly depressed, is called 

 thefovea centralis, or central pit of the retina. 

 It is constituted entirely of the cone-like ter- 

 minations of the nerve-threads, relatively small 

 in size and closely packed together, while 

 around it is a less compact arrangement of the 

 cone-like and rod-like terminations. Hence the 

 visual picture is defined with consummate clear- 

 ness only at this point, and presents a depart- 

 ure from the camera in the shape of an intensi- 

 fication of its chief defect, which in the eye thus 

 becomes a part of its exquisite perfection, for 

 the large area upon which the light falls affords 

 a wide field of impression sufficiently sensitive 

 to give notice of the presence of the objects 

 which are reflected upon it, while the fine 

 mechanism by which the eye is moved with a 

 facility, quickness, and accuracy that are mar- 

 velous, brings the slight area of perfect vision 

 to bear upon the particular object to be scruti- 

 nized or the different parts of that which is 

 merely looked at. Therefore, we have practi- 

 cally combined perfect distinctness of the vis- 

 ual picture and a wide field for its reception. 

 The camera fixes its glance upon a narrow field, 

 and forms a picture with a clear center and 



