436 
PROCEEDINGS OF THE SOCIETY. 
critical days. The milled heads of the mechanical stage seemed incon- 
veniently large, especially when compared with those of Zeiss’s stage 
that was shown that evening. The centering motions of the substage 
seemed to be of an ordinary cheap type, that could hardly be compared 
with the best right-angled motions known. The stud at the back of the 
Jackson limb for fixing the Microscope on a support when used for 
photography was evidently suggested by Swift’s Microscope, to which 
reference had been made. 
Mr. Mayall concluded by expressing his regret that Dr. Van 
Heurck’s specification should have resulted in the production of the 
Microscope exhibited. In view of the enormous number of Microscopes 
that had been figured and described in the various text-books, and in the 
Journal of the Society, it appeared to him that Dr. Van Heurck had 
made a most inferior selection of points for his specification, resulting in 
an instrument the design of which he (Mr. Mayall) regarded as much 
below the standard claimed for it by Dr. Van Heurck. 
Mr. E. M. Nelson said that as regarded the method of working the 
fine-adjustment of the substage, he agreed with Mr. Mayall that the 
position of this head was inconvenient, and it might also easily interfere 
with the rotation of the stage; indeed, he hardly knew why it was 
wanted at all, because when once the substage was focused it was done 
with and remained the same through the rest of the operations, whereas 
the other adjustments were being worked almost continually. He thought, 
therefore, that it would be an improvement if it was put on the other 
side of the Microscope, and on the under side, so as not to impede the 
rotation of the main stage. 
Mr. Watson said he had heard the criticisms which had been made, but 
would take one exception to them all — namely, that no one could properly 
judge of any Microscope unless he had tried it ; and because it 
happened that Mr. Mayall once had a Zentmayer Microscope and it 
went wrong, he was not prepared to admit that therefore no others 
would keep right, knowing, as he did, how many of similar construction 
he had made and sold without even one ever being returned as faulty. 
As to the No. 1 Zentmayer model, he could quite understand how it was 
possible for that to work loose and become useless ; but as regarded 
such as were made in the same w r ay as the one before the meeting, he 
had demonstrated to his own satisfaction that it was quite possible to 
make a Microscope in which the adjustments were perfectly firm, and 
would remain so with any amount of ordinary usage. Dr. Van Heurck 
in ordering this form did not do so without experience, but gave as his 
reason that the Microscope with which he was supplied by their firm, 
and in which the principal points were the same, had been in use for 
three or four years, and was now as good as ever. In his letter to them 
he said that he had Microscopes in his possession by all the best 
English and Continental makers ; but the one he had from them had 
proved to be so satisfactory that it was preferred for use to any other. 
He thought that in matters of this kind an ounce of practice was worth 
any amount of theory, and for his part he did not see why, if an English- 
man brought out a Microscope, because some one in another country 
made something like it which was bad, therefore, the English article 
was to be condemned. As to the substage adjustment, that had also 
