444 



subject to whatever uncertainty remains with regard to astronomical 

 refraction. 



As the Astronomer Royal has not been in possession of the instru- 

 ment a sufficient length of time for deducing the real quantity of re- 

 fraction from his own observations, he has hitherto employed those 

 of Dr. Bradley, which have been many years in use at the Royal Ob- 

 servatory ; but he observes, that any alteration which may be here- 

 after found necessary, may easily be made as correction to the above 

 observations. 



Observations relative to the near and distant Sight of different Persons. 

 By James Ware, Esq. F.R.S. Read November 19, 1812. [Phil. 

 Trans. 1813, p. 31.] 



The author states, in the first place, that he has rarely observed 

 short-sightedness in children under ten years of age, and that he con- 

 siders it as commencing generally between that period and eighteen; 

 that it at first occasions so little inconvenience, that it is not noticed 

 by those who have not access to concave glasses, and consequently 

 is very frequently overcome by the natural efforts of the eye. Per- 

 sons, on the contrary, in the higher ranks of society, who have it 

 more in their power to indulge a slight weakness, by having recourse 

 to short-sighted glasses, soon confirm the imperfection, and in many 

 instances even render it worse, by employing glasses deeper than are 

 necessary. 



For the purpose of instituting a comparison between the propor- 

 tional prevalence of this defect in different classes of society, Mr. Ware 

 made inquiry in the three regiments of Foot Guards, containing nearly 

 10,000 men, and also in the two Universities, Oxford and Cambridge. 

 In the Guards short-sightedness among the privates is scarcely known; 

 and not more than half a dozen recruits are said to have been re- 

 jected for this imperfection in the -course of twenty years. In the 

 Universities, on the contrary, the numbers are so considerable, that 

 in one of the colleges in Oxford, it is said that of 127 persons, so 

 many as thirty-two have used either a hand-glass or spectacles. It is 

 thus proved that short-sightedness is corrected in one class of per- 

 sons, and encouraged in the other ; and it is evident that even in 

 those who absolutely require glasses, it may be increased by using 

 such as are deeper than are really necessary, or counteracted by em- 

 ploying the lowest with which the eye can see with comfort. 



It is observed, however, that extreme short-sightedness sometimes 

 occurs in children from visible imperfection in the form of the cor- 

 nea, and sometimes arises as an accidental and temporary conse- 

 quence of general debility, and is then removable by chalybeate me- 

 dicines and bracing applications. 



Dr. Porterfield has observed, that the pupils of short-sighted per- 

 sons are in general more dilated than those of others ; but Mr. Ware 

 does not admit this to be generally the case ; neither does he admit 



