958 BECORD OF CURRENT RESEARCHES, ETC. 



which can be turned either by hand, or, when a higher speed is 

 required, driven by a treadle and pulley. The saw is provided with 

 adjustments to secure its parallelism and proper tension ; the section 

 is regulated by a screw of fifty threads to the inch, reading to thou- 

 sandths by means of a micrometer head ; the feed is either automatic 

 by means of a cup, in which a suitable quantity of shot can be placed, 

 acting by gravitation on a lever ; or, as Dr. Matthews j)refers, is 

 capable of being regulated by hand. Owing to the steady motion of 

 the saw when in proper adjustment, sections of suitable tissues can be 

 cut as thin as the thousandth of an inch ; the surfaces show no trace 

 of the saw-cut, and are almost jjolished ; very little after-treatment is 

 needed to remove the few scratches left by the saw, and if required 

 for mounting in balsam it can be done at once, taking the usual pre- 

 cautions to prevent penetration, and the consequent obliteration of 

 structure. 



Zeiss' tV Objective. — Colonel Woodward's views on this will be 

 found at p. 988 of the ' Proceedings.' 



Micrometry. — A reference to this subject will be found at p. 988 

 of the ' Proceedings.' 



