311 



NOTES. 



ON A METHOD OF MARKING A GIVEN OBJECT FOR 

 FUTURE REFERENCE ON A MOUNTED SLIDE. 



By James Burton. 



{Read November 25th, 1913.) 



Most likely all of us at times have come across some particular 

 object on a mounted slide which we have felt we should like to be 

 able to find on another occasion ; perhaps some special diatom on 

 a strewn slide, for instance. Now there are several methods of 

 doing this, and a little piece of apparatus is sold by the opticians 

 which marks a circle round an object first found under the micro- 

 scope. But perhaps with the majority the necessity does not 

 occur often enough for it to be worth while to keep a special tool, 

 and the little dodge, if I may call it so, which is here described 

 can be carried out without any other instrument than those we 

 most of us already have and use. If the object to be marked is 

 sufficiently large for recognition under a moderate power, such as 

 can be obtained with a hand lens or dissecting microscope, the 

 matter is very simple. First find the object, then with a fine 

 camel-hair or sable brush carefully place a dot of water-colour 

 over it large enough to be seen with the naked eye, set it on one 

 side to dry ; when dry, put the slide on the turn-table with the 

 dot accurately in the centre and turn a small ring round it with 

 any dark cement you may have in use; when this is hard, which 

 will depend on the kind of cement used, the water-colour can be 

 removed with a damp brush, and the cover can be carefully 

 cleaned with a piece of soft rag. 



If the object, however, is too small to be readily recognised 

 without a high power, as, of course, is usually the case, for 

 it is not necessary to mark anything but minute objects, 

 a rather more complicated variety of the same plan should 

 be adopted. Again first find the object with a suitable 

 power, such as a | inch or ^th inch, and let the specimen be as 



