val) THE MICROSCOPE. 
‘was made in an unexpected way. Some years ago I packed my col- 
lection, numbering at that time many hundred mounts, in a trunk, 
and took it with me on my wanderings. Altogether the collection 
traveled between 15,000 and 20,000 miles, mostly by rail. It fared 
badly, but I consider the loss as slight in comparison with what it 
taught me regarding the powers of endurance of the various cements, 
media, etc. For obvious reasons it is impossible to give exact fig- 
ures and I can only give the general result. There were only a few 
slides or covers broken, but the number of mounts ruined by the 
covers coming off or separating so that air entered was very large. 
The cements which stood this test the best were gold size and the 
solid marine glue. Balsam mounts, which were strengthened by a 
ring of varnish, were but little affected, while those not so protected 
suffered greatly. None of the wax cells made, as described later on, 
lost their covers or separated from the slide, while a large number of 
those made by cementing rings of wax to the slide were spoiled. 
Shellac, not backed up by a tougher cement, gave out in almost 
every instance. 
Gold size has been a favorite cement with me for a long time. 
Some eight years ago I procured a number of bottles from the 
Messrs. Queen & Co., and some that is still left seems stronger than 
when first bought. Gold size is simply linseed oil rendered very 
“drying.” There are, however, a number of different formule for 
its preparation, and when you find a sample that is of more than 
ordinary worth it is well to lay in a supply. The same holds true 
of all such material as is not liable to deteriorate with age. Gold 
size hardens by oxydation, and very slowly at that, soa sufficient 
length of time must be allowed for each coat to become hard. If it 
were not for the slowness with which it hardens it would make an 
admirable cell. As it must be applied in very thin layers it takes too 
long to make cells of any gieat depth, and unless they are carefully 
made they will eventually break down. I use gold size for dry 
mounts, to attach metal cells, to ‘back up” a more brittle cement, 
and, in fact, in all cases where it is possible to do so. 
Another cement, which works well with me, is Shellac. It must 
be the genuine article, and not the resin compound that is frequently 
sold for it. Shellac I prepare as follows: Put a few scales of orange 
lac in a wide-mouthed bottle and cover with 95 per cent. alcohol. 
The bottle is placed in a water-bath and a gentle heat applied until 
the shellac is dissolved, when it is filtered through muslin or absorb- 
ent cotton, previously moistened with alcohol. If too thick, add 
more alcohol and continue the heating for a short time. The shellac 
