130 ON COLLECTING AND PRESERVING FOSSILS. 
in an oven, and hardened by treatment while still warm with a weak 
solution of gum-tragacanth. This is better than gum-arabic, because 
it does not leave a glossy surface. 
2. Fossil leaves in clay curl up on drying, and are frequently 
destroyed. These may also be preserved by the application of gum- 
tragacanth or a thin solution of gelatine. 
3. Friable bones are best hardened by first warming, and then 
dipping for a few moments in a warm, weak solution of gelatine. 
4. Pyritized fossils cannot always be preserved. When decaying, 
allow them to soak for some time in water to dissolve the sulphate 
of iron ; then dry carefully, and dip them while warm in melted 
paraffin wax. 
5. Ordinary gum, with a little glycerine or glue, may be used for 
mending small specimens. Shellac is too brittle for most purposes. 
The best cement for large specimens is liquid glue, with a small 
admixture of plaster of Paris. Dental cement is very useful, 
especially when it is desired to fix a fragment so that it can be 
separated again. 
Packing Fossils. 
1. In packing fossils always use flexible material, such as crumpled 
paper, shavings, straw, moss, grass, or cotton-wool — never sawdust, 
sand, or grain (chaff). Boxes should be tightly packed, leaving no 
room for shifting of contents. 
2. Boxes are better small and numerous than large and few. 
Heavy cases suffer more from concussion in transport than small 
boxes. 
Small boxes, carefully packed and placed in a larger case, will 
travel well. 
The opening of cases by Customs officers in docks* and on the 
frontier of foreign states is often more fatal than a very long journey 
to the contents of boxes. Bribery in such cases seems permissible, 
to ensure lenient treatment of collections. 
* If addressed "To the Director of the British Museum (Natural History), 
Cromwell Jioad, London, 8.W.," the cases will not be opened by the Customs 
officers, but xent on at once under seal. 
