( 173 ) 



IV. — The President's Address. 

 By Prof. P. Martin Duncan, F.R.S., V.P.L.S., &c. 



(^Annual Meeting, l^th February, 1884,) 



The two addresses wliich I have had the honour of deKvering as 

 your President, were mainly devoted to the consideration of the 

 practical optics of objectives of high power. On the present 

 occasion I desire to direct attention, amongst other matters, to the 

 importance of the perfection and use of those combinations of 

 lenses which do not amplify greatly, and yet are more frequently 

 employed than high powers and quite as usefully. 



The combinations which give large amplification, are doubtless 

 very attractive to the high-class microscopist, who prides himself 

 on overcoming the difficulties attending the employment of his 

 objectives, and they are of course absolutely requisite in most 

 microscopical investigations. But the low powers — so readily and 

 easily managed, so necessary before the employment of the high- 

 power objective is attempted, so important in the use of the 

 binocular Microscope and of the polarizing apparatus, and such 

 auxiliaries to the hand-lens, from the readiness with which opaque 

 objects can be viewed — are of paramount importance to microscopists 

 of every degree. 



There are many microscopists who enjoy the use of their 

 instruments without any desire or power to add to the original 

 research which accumulates so seriously year by year. They like 

 to see beautiful things, to marvel at the aesthetics of nature, to 

 examine the intricacies and delicacies and exquisite symmetry of 

 the structures of natural objects which so far surpass the results of 

 the art and industry of man. To all these followers of our science 

 the low-power objective is of primary importance. Many hundred 

 lithographic plates are published, year by year, on which are 

 depicted minute recent and fossil forms which could not be studied 

 without the low-power objective, and which do not come within 

 the scope of high amplification. As being necessary to the most 

 advanced investigators of minute things in their preliminary work, 

 as absolutely necessary for the draughtsman and describer of opaque 

 and transparent small objects, and as the media of great intellectual 

 enjoyment, the objectives which are termed low in power, from 

 their magnifying capacity being small, and which have from 

 1/2 in. to 4 in. of focus, should always receive attention. They 

 illustrate the supreme ease with which former weary labour has 

 been superseded. 



A good monocular or binocular stand, a large and movable 



