20 



Dr. T. L. Llewellyn. 



[Dec. 19, 



certifying surgeon of that district, and he told me that he had more cases 

 of nystagmus from that small colliery than from all the other collieries 

 around. In another district I had many complaints that the lamps were 

 not well cleaned. Here, again, the percentage was above the average. In 

 several collieries where the average was high, the lamps were cleaned by 

 hand, a very inefficient proceeding compared with the machine cleaning. 



Table XVI.— Oil used in 43 Collieries. 





No. of pits. 



Percentage of nystagmus. 





16 (14 entirely) 



0-58 





4(3 „ ) 



0-68 





6(5 „ ) 



71 





15 (14 „ ) 



9(8 „ ) 



0-81 





0-93 



Lamps compared with the standard candle (Eeport of Mines Accident 

 Commission, 24) : — 



Davy 0'19 



Clanny 0"62 



Mueseler 0'69 



Marsaut 0-68 



We do not realise how much of our light is due to diffused reflecting 

 power of the walls of any building we happen to be in. In the coal mine 

 practically all the light is absorbed. 



Ocular Defects. 



This introduces the personal factor of the disease, and one which has 

 been too much neglected in the past. It has always struck me as strange 

 that when two men are working together under similar circumstances one 

 may be affected and the other left. I have examined men who have been 

 underground for 60 years without showing any sign of nystagmus. Yet a 

 case may develop after six months' underground life (Case 19). 



The disease has been shown to attack the men who use their eyes the 

 most in a much larger proportion than the other men. 



My figures are incomplete, but they show that a large proportion of men 

 suffer from error of refraction. T. Thompson (20) brings out this point, 

 but his cases are few. Eomiee also says (2) that a large proportion are 

 hypermetropics, but in his later communications does not lay much stress 

 on this point. Dransart (5) and Snell (17) say that the majority of cases 

 are normal. 



