PROCEEDINGS OF THE SOCIETY. 423 



its exhibition as a working apparatus in the meeting hall would nol 

 show the actual calibration capacity. 



Mr. Spitta said that they had just listened to a most interesting 

 series of remarks ; to him, however, the great difficulty seemed to be the 

 enormous amount of practice required in the use of such an apparatus. 

 It would, no doubt, appear easy enough to one who, like Mr. Beck, was 

 facile princ&ps in the work, but there were difficulties connected with its 

 use which to many seemed almost insurmountable ; his own chief 

 stumbling block, for instance, lay in the fact that there was no fixed 

 standard, a difficulty which had especially appealed to him in dealing 

 with the MacMahon micrometer. The main point, however, in all this 

 class of work was, of course, to gain experience in the instrument which 

 was being used, and at present they were not quite satisfied with their 

 own experience. 



Mr. Beck said that the MacMahon class of interferometer presented 

 infinitely greater difficulties than an instrument capable of measuring 

 a Grayson's micrometer. It was quite easy to count the number of wave- 

 lengths in a distance of T ^ in. or T £- lT mm., but it would obviously not 

 be possible to count the number of wave-lengths in a yard with any 

 success. The measurement had to be made by a step-by-step method, 

 counting only the differences at each step. He thought that so far as 

 calibrating a stage-micrometer went, the matter was comparatively simple 

 so long as a sufficient amount of time were given to it. 



The President said that Mr. Beck's method certainly sounded more 

 tempting than that which entailed the enormous amount of labour spent 

 by Mr. "Spitta on this matter. He imagined that when Mr. Grayson 

 had made his new screw, however, there would be still more work for 

 Mr. Spitta. He considered that the very heartiest thanks of the Society 

 should be accorded to Mr. Spitta for the great trouble he had taken over 

 this important question. 



The vote of thanks was carried with acclamation. 



Mr. E. J. Sheppard read a communication on "The Re-appearance 

 of the Nucleolus in Mitosis." 



The President regretted that there was no time that evening to discuss 

 many points of interest in Mr. Sheppard's paper, but wished to propose 

 a very hearty vote of thanks for his communication; this was carried 

 unanimously. ' 



Dr. Eyre, in announcing a paper by Senor Domingo de Orueta on 

 "Apparatus for Photomicrography with the Microscope standing in any 

 position, especially in the Inclined Position,'' said that he would merely 

 select for reading a few passages which appeared to him to present 

 the salient features of the communication, leaving out those portions 

 which dealt with the mechanism of the apparatus. The writer com- 

 menced by remarking on the inconvenience of having to carry the Micro- 

 scope away from the working bench to the optical bench, in order to take 

 a microphotograph, and discussed the difficulties of moving the apparatus ; 

 he then went on to describe a Microscope camera of his own design. 



