ANIMALS. 



to;* 



has always found that the best eye saw every 

 object the largest. This he ascribes to ha- 

 bit; for near-sighted people being accustom- 

 ed to come close to the object, and view but 

 a small part of it at a time, the habit ensues, 

 when the whole of an object is seen, and it 

 appears less to them than to others. 



Infants, having their eyes less than those 

 of adults, must see objects also smaller in pro- 

 portion. For the image formed on the back 

 of the eye will be large, as the eye is capaci- 

 ous ; and infants, having it not so great, can- 

 not have so large a picture of the object. 

 This may be a reason also why they are un- 

 able to see so distinctly, or at such distances, 

 as persons arrived at maturity. 



Old men, on the contrary, see bodies close 

 to them very indistinctly, but bodies at a great 

 distance from them with more precision; and 

 this may happen from an alteration in the 

 coats, or, perhaps, humours of the eye ; and 

 not, as is supposed, from their diminution. 

 The cornea, for instance, may become too ri- 

 gid to adapt itself, and take a proper convexi- 

 ty for seeing minute objects ; and its very 

 flatness will be sufficient tofit it fordistant vision. 



When we cast our eyes upon an object ex- 

 tremely brilliant, or when we fix and detain 

 them too long upon the same object, the organ 

 is hurt and fatigued, its vision becomes indis- 

 tinct, and the image of the body which has 

 thus too violently, or too perseveringly em- 

 ployed us, is painted upon every thing we 

 look at, and mixes with every object that oc- 

 curs. " And this is an obvious consequence 

 of the eye taking in too much light, either im- 

 mediately, or by reflection. Every body ex- 

 posed to the light, for a time, drinks in a quan- 

 tity of its rays, which being brought into dark- 

 ness, it cannot instantly discharge. Thus the 

 hand, if it be exposed to broad day-light for 

 some time, and then immediately snatched 

 into a dark room, will appear still lumi- 

 nous : and it will be some time before it is to- 

 tally darkened. It is thus with the eye; 

 which, either by an instant gaze at the sun, 

 or a steady continuance upon some less bril- 

 liant object, has taken in too much light ; its 

 humours are, for a while, unfit for vision, until 

 that be discharged, and room made for rays 

 of a milder nature." How dangerous the look- 

 ing upon bright and luminous objects is to the 



NO. 15 & 16 



sight, may be easily seen, from such as live 

 in countries covered for most part of the year 

 with snow, who become generally blind beibre 

 their time. Travellers who cross these coun- 

 tries are obliged to wear a crape before their 

 faces, to save their eyes, which would other- 

 wise be rendered totally unserviceable ; and 

 it is equally dangerous in the sandy plains of 

 Africa. The reflection of the light is there so 

 strong, that it is impossible to sustain the effect 

 without incurring the danger of losing one's 

 sight entirely. Such persons, therefore, as 

 read or write for any continuance, should 

 choose a moderate light, in order to save their 

 eyes ; and although it may seem insufficient al 

 first, the eye will accustom itself to the shade, 

 by degrees, and be less hurt by the want of 

 light than the excess. 



" It is, indeed, surprising how far the eye 

 can accommodate itself to darkness, and make 

 the best of a gloomy situation. When first 

 taken from the light, and brought into a dark 

 room, all things disappear; or, if any thing 

 is seen, it is only the remaining radiations that 

 still continue in the eye. But, after a very 

 little time, when these are spent, the eye 

 takes the advantage of the smallest ray that 

 happens to enter ; and this alone would, in time, 

 serve for many of the purposes of life. There 

 was a gentleman of great courage and under- 

 standing, who was a major under King 

 Charles I. ; this unfortunate man, sharing in 

 his master's misfortunes, and being forced 

 abroad, ventured at Madrid to do his king 

 a signal service ; but unluckily failed in the 

 attempt. In consequence of this, he was in- 

 stantly ordered to a dark and dismal dun- 

 geon, into which the light never entered, and 

 into which there was no opening but by a 

 hole at the top, down which the keeper put 

 his provisions, and presently closed it again 

 on the other side. In this manner the unfor- 

 tunate loyalist continued for some weeks, dis- 

 tressed and disconsolate ; but at last he be- 

 gan to think he saw some little glimmering of 

 light. This internal dawn seemed to in- 

 crease from time to time, so that he could not 

 only discover the parts of his bed, and such 

 other large objects, but, at length, he even 

 began to perceive the mice that frequented 

 his cell ; and saw them as they ran about the 

 floor, eating the crumbs of bread that happen- 



2H 



