THE president's ADDRESS. 99 



and just in proportion as it sympathises in accommodation and ad- 

 justment with its fellow, is it out of accord with its own proper 

 condition. This is true, whether it be closed, as is sometimes the 

 case, or open and gazing at vacuity. By and bye the unused eye 

 ceases to a certain extent to sympathise with its fellow. Still later, 

 the fault which has thus arisen incidentally may become habitual. 

 In this manner the constant use of the monocular micros- 

 cope may tend to break the consentaneity of action of the two 

 eyes, and so lead to impairment of perfect vision. It is clear that 

 such a result arising from such cause may be in great part, if not 

 yrholly, obviated by using both eyes at the same time under the 

 same conditions. We do this when we look through a rightly ad- 

 justed binocular microscope. It is not, then, so much for the sake 

 of the greater beauty of the view, as for the sake of saving the 

 eyes that I urge so strongly the use of the binocular in every 

 case in which the power it bears is high enough for the observa- 

 tion to be made. 



It seems to me that since the invention, and I may almost say 

 the perfection of the achromatic objective, no service has been 

 rendered to microscopists at all equal in value to the introduction 

 by Mr. "Wenham of his stereoscopic binocular arrangement. Those 

 eminent men who first made for us the achromatic objectives have 

 enabled us to see what otherwise might still have been beyond our 

 ken; and Mr. Wenham has done much to save our eyes. The 

 one great drawback to Mr. Wenham's arrangement is, as you all 

 know, that it cannot be used with the higher powers : and yet it 

 is with such that we want the binocular most, for they are most 

 trying to the eyes. 



I should do wrong if I omitted to allude to the binocular 

 arrangement for high powers invented by Messrs. Powell and Lea- 

 land: all honour to them for what they have done. Most of us 

 have seen various objects shewn by these gentlemen under their 

 arrangement ; and all who have seen such objects must have been 

 struck by the admirable manner in which they were displayed. But 

 the arrangement of Messrs. Powell and Lealand has a defect, 

 which, from what I have said, you will readily understand seems to 

 me more important than it may seem to some — perhaps more im- 

 portant than it really is. The defect to which I allude is this : 

 there is a very great difference in the amount of light transmitted 

 to the eyes — one receives much more than the other. Further, I 



