242 The Philippine Journal of Science wis 



THE SQUARE-RULED MICROMETER USED AS A POSITION INDICATOR 



For the purpose of referring to specific parts of the micro- 

 scope field in the discussion of objects in view under the com- 

 pound microscope, the square-ruled ocular micrometer scale is 

 in some ways superior to the field pointer. When so using the 

 scale I assign numbers to the transverse rows of squares and 

 letters to the vertical rows so that each small square in the 

 scale may be specifically indicated by a number with a letter. 

 The Zeiss scales that I use are not marked with numbers. If 

 the scales were to be so marked I would prefer that the trans- 

 verse rows be numbered and the vertical rows lettered. The 

 obvious advantage of using this accessory instead of a field 

 pointer is that many different parts of the field can be indicated 

 without readjustment of the apparatus. 



THE SQUARE-RULED MICROMETER FOR DRAWING TO SCALE 



For use in drawing to scale from the compound microscope 

 all students in my classes in botany and pharmacognosy since 

 1911 have been supplied with square-ruled ocular micrometers. 

 I have found it convenient to use for the drawing a thin * semi- 

 transparent paper of suitable texture, and to place under it a 

 paper scale ruled into squares corresponding to those of the 

 ocular scale. Using a Zeiss No. 3 huygenian micrometer ocular 

 containing a micrometer disk with a 5 mm square ruled at 0.5 

 mm intervals each way and a paper scale 90 mm square ruled 

 at 9 mm intervals, magnifications of 120 and 500 diameters 

 are obtained with the Zeiss achromatic objectives A and D, 

 respectively. As paper scales for any desired magnification 

 can be easily provided, this method affords unrestricted choice 

 within a greater range of available magnifications than can be 

 had with a camera lucida. The dimming of the microscope 

 image and the complication of light adjustments attendant on 

 the use of the Abbe camera lucida are avoided by the use of 

 the square micrometer as an aid in drawing. And the expense 

 of equipment and deterioration is comparatively insignificant. 



CAPILLARY GLASS RODS FOR COVER-GLASS SUPPORTS 



In making Venetian-turpentine mounts of delicate objects as 

 variable in size as the Volvocaceae it is desirable to have cover- 

 glass supports of greater range of thickness than is afforded 



'The use of a translucent drawing table illuminated from below, with 

 the s quar e- ru ied scale on thin paper or on the glass of the table, would 

 make it possible to use thicker drawing paper. 



