126 PROCEEDINGS OF THE SOCIETY. 



so that your wishes could be obtained as to whether you would not like 

 to offer some expression of sympathy with the relatives of Dr. Dallinger, 

 seeing he has had such a lengthy and illustrious connection with our 

 Society. The Council have already passed a resolution to this effect, 

 but I repeat it has been thought you might very possibly desire — nay, 

 even more, would very likely have considered it an omission on then- 

 part had they not offered you the opportunity of joining in the same. 

 Is it then your pleasure, gentlemen, that the Secretary be requested to 

 write a suitable letter of condolence to the family, expressing your 

 sympathy with them in their bereavement, and assuring them at the 

 same time of the loss you feel the Society has sustained by the death of 

 so illustrious a Fellow ? 



The motion for a vote of sympathy with the family of the late 

 Dr. Dallinger was then put to the Meeting, and carried unanimously. 



Mr. A. A. C. E. Merlin's paper " On the Measurement of Grayson's 

 K) Band Plate," was read to the Meeting by Mr. F. S. Scales. 



Mr. Rheinberg said the high degree of accuracy attained in the 

 rulings of these lines was sufficiently marvellous, and although it might 

 sound curious to say so, he considered it a positive advantage that an 

 absolute accuracy could not be attained, as in the use of these gratings 

 both for testiug the resolving powers of objectives and for diffraction 

 experiments the appearances resulting from the slight deviations from 

 absolute accuracy were particularly helpful to forming one's conclusions. 



Mr. Shillington Scales said he did not quite see how Mr. Merlin 

 managed to make measurements of such small degree, because the 

 ordinary micrometer wire was considerably coarser than some of the 

 measurements given, even with the highest magnifications, and would in 

 such minute divisions more than cover the object it was wished to 

 measure. He had met with this difficulty himself in making measure- 

 ments of less than 0"25/x, and should like to understand how it was got 

 over. • 



Mr. A. E. Conrady said there would, no doubt, be a considerable 

 difficulty in obtaining the measurements of a very minute single object, 

 but Mr. Merlin worked upon several objects, and in that case it was 

 posssible to estimate distances very accurately when a line came between 

 two or three other lines, and the accuracy with which measurements 

 could then be made was quite astonishing. This would be very possible 

 in the case of one-third of a micron, or one-thousandth of a millimetre ; 

 but when one spoke of two-millionths of an inch, it looked like a subject 

 for discount. 



The Chairman said it would be, he thought, a good institution if 

 when a new Fellow joined the Society his friends should introduce 

 liim to the Secretaries and to other prominent members present, so that 

 he should rapidly become acquainted with them all. He mentioned 

 this because it had been brought before his notice that some new 

 Fellows had complained very naturally they felt dull and strange at the 

 Meetings, which was very foreign, he felt sure, to the wishes of those 

 present. It had also been brought before him to mention that the 

 Sectional Meetings of the Society were held on the first and fourth 

 Wednesday evenings in the month, and that it would be an encourage- 



