1000 PEOCEEDINGS OF THE SOCIETY. 



powerful planing machines, to whicli a perfectly true motion combined 

 with a powerful grip was an essential qualification. He also 

 explained a new form of fine adjustment whicli Messrs. Swift had 

 applied to the same instrument. 



Mr. Crisp exhibited the Geneva Company's Microscope Callipers 

 {ante, p. 796), an instrument for measuring very minute thicknesses 

 up to 1/1200 mm. 



Mr. J. Mayall, jun., said that Mr. A. Y. Moore had forwarded a 

 slide of Amphipleura pellucida which was worth remark. It looked 

 as if the diatoms had been burnt on the cover-glass in the usual way, 

 and that then a coating of silver had been deposited upon them. The 

 object gave the strongest and best image with the vertical illuminator 

 that he had ever seen. He could not explain why it was so without 

 further examination ; but Mr. Powell had brought a Microscope for 

 the purpose of showing it, so that the Fellows would have an oppor- 

 tunity of examining it for themselves. 



Mr. Crisp said that the slide was no doubt mounted in the way 

 recently published by Mr. Moore (ante, p. 829), viz. by coating one 

 side with pure silver, increasing its visibility more than four times. 



Mr. Mayall said he might venture to state that he had examined 

 the slide with an objective of very large aperture and did not see the 

 dots as described by Mr. Moore. 



Prof. Bell exhibited specimens of Crustacea which had been sent 

 by Mr. Bolton — Leptodora and Argulus — and made some remarks 

 descriptive of the animals and their habits. 



Mr. Crisp exhibited Mr. Griffith's ingenious turn-table, described 

 (but not exhibited) at the June meeting (ante, p. 826). 



Prof. Bell said he did not know whether it was the case that any 

 of the Fellows of the Society had not yet been to one of the most 

 interesting and instructive exhibitions which had been offered to 

 their notice, but if so, he would strongly recommend them to repair 

 the omission while the opportunity remained, and pay a visit to 

 room No. 15 of the City and Guilds' Institute to see what Mr. Watson 

 Cheyne had prepared in the way of Bacteria and their various modes 

 of propagation in their proper media (see p. 808). He thought it 

 desirable to mention the matter, because the time for the close of the 

 exhibition was now getting short. Mr. Cheyne gave a demonstration 

 on Thursdays at 4 o'clock. He hoped that the value of the exhibi- 

 tion would before long be more fully recognized, and that it might 

 lead to the establishment of some such systematic experiments and 

 researches as those carried on by Dr. Koch under the auspices of the 

 German Government. 



Mr. Cheshire said he was glad that Prof. Bell had drawn atten- 

 tion to this matter. He had recently found some specimens which 

 were very peculiar, and which he had given to Mr. Cheyne, who was 



