ZOOLOGY AND BOTANY, MICROSOOPY, ETC. 



693 



for the first time wish to know the natural size of the object exhibited, and 

 for all opaque objects which could be mounted on a white, black, or 

 coloured background, this information can be best attained by printing on 

 the ground a scale ruled, say, one hundred lines to the inch, and upon which 

 the object can be mounted, when its size will be at once apparent. I have 

 engraved and brought down for presentation to the Society a ruled plate 

 and other requisites, which will enable those members who care to do so, to 

 produce any number of scales required. The plate before being used 

 should be cleaned with turpentine, and the colouring matter rubbed in 

 dry, lampblack, or any other powder colour will do, the excess colour 

 being wiped off by passing a piece of tightly wrapped wash-leather across 

 the plate. A piece of smooth wood or glass should then be taken, and 

 Boap or bees'-wax drawn across the face, and the paper about to be printed 

 on should be laid upon it, the soap making it adhere to the face and 

 keeping it straight. The soap or wax should then be passed over the 

 paper, taking care to have a smooth and even film. The paper being thus 

 prepared should be placed on the plate and the back rubbed lightly with 

 the steel burnisher provided, and, on removing it, a clear impression of 

 the scale will be found imprinted on the surface. If ordinary note-paper 

 be used, many objects can be well illuminated by sending light through 

 from the mirror of the Microscope. I have also engraved for the Society 

 a metal micrometer ruled 100, 250, 500, and 1000 lines to the inch, which 

 the members will find useful for measuring opaque objects. It has the 

 advantage of not being so liable to break as the glass micrometers, and can 

 be readily used with all powers up to 1/6 in. objective." 



Cover-glass Holder,* — Dr. F. L. James describes the device (fig. 199) 

 for holding cover-glasses after they are cleaned and ready for application 

 to the slip. It consists of a coil of brass spiral spring wire bent round a 



Fig. 199. 



Spbral Vlre^ 

 Sirring 



WW' 



Cork 



cork, which has been grooved to receive it. The method of using is illus- 

 trated by the cover-glasses in position on it. 



Pmc. Amer. Soc. Micr. 9tli Ann. Meeting, 1880, p. 145 (2 figs.)- 



