1926 



Journal of Applied Microscopy 



image is done with a focusing eye-piece (J) set on the clear spot in the ground 

 glass and is obtained by the use of the slow-motion screw of the microscope. 



Slow isochromatic plates have proven the most satisfactory for all around 

 use, as they give the color values without the use of a color screen, thus avoiding 

 long exposures, with their attendant ills, vibration of the optical bench and irreg- 

 ularity in illumination. 



With an electric arc light of about 2000 candle power, a system of good con- 

 densers, a prism reflector, and using a magnification of 65 diameters, an exposure 

 need not be longer than twelve seconds. Developed with ordinary pyro devel- 

 oper, a negative giving good, contrasty prints should be obtained. A glossy 

 paper should be used to reproduce a micro-negative. 



If it is desired to preserve the micro-section it should be coated with a solu- 

 tion of paraffin in benzole and placed under a bell jar or in an air-tight case 

 containing a vessel filled with calcium chloride or other hygroscopic substance. 



To be of practical value a complete record should be kept of the history of 

 the metal examined, embracing its chemical composition, its treatment with 

 regard to heating and forging, the results of the physical tests, nature of the 

 etching solution employed, magnification and illumination used, and any other 

 related facts that may be considered of importance. Special pains should be 

 taken to clearly state the location of the micro-section in the original piece of 

 metal and whether the surface photographed is longitudinal or transverse. Card 

 index files are published, which make possible the combination of the mounted 

 micro-photograph with all of the data mentioned. 

 South Bethlehem, Pa. M. A. RiCHARDS. 



t 



Double Mounting for Whole Objects. 



It is frequently desirable to have a small object mounted in such a way as to 

 be readily studied from both surfaces. The plan of mounting on a large cover- 

 glass with a smaller slip used as a cover has been in use for some time. The 

 usual method was to fasten the larger, or bottom, slip upon an ordinary micro- 

 scopical slide by bits of gummed paper, 

 and when it was necessary to examine 

 the lower surface of the object the bits 

 of label were cut in two, the thin glasses 

 turned over, and then replaced with 

 other stickers. This left the object in 

 danger of injury while unmounted, and was clumsy. I want to suggest a " new 

 wrinkle," which I have never seen used or described, although it may be old to 

 some microscopists. Gum one end only of the larger cover-slip to the slide by 

 a piece of label, or better, of sticking plaster, and let this serve as a hinge, so 

 that the covers can be turned back, past the end of the slide. A small wire 

 clip, half of a Niagara clip for instance, is then used to hold the covers firmly 

 to the slide, in either position. This is a safer, quicker, and neater method 

 than the old one. » H. F. Perkins. 



Johns Hopkins University. 



