1896. THE PREPARATION OF CHALK FOSSILS. 305 



robust brachiopods, there is nothing to be gained by the use of water, 

 as both matrix and fossil are much more fragile when wet. An 

 indispensable article in every workshop is an irrigator, and the thing 

 is both cheap and simple. All that is wanted is a pail with a short 

 half-inch leaden pipe soldered into it near the bottom. To this is 

 attached a rubber tube, armed with a glass irrigator-point, and con- 

 trolled by a spring clip. Any surgical instrument-maker will supply 

 the two last for a few pence. If the pail is placed on a shelf, three or 

 four feet above the level of the bench, a good stream is secured. By 

 means of this simple contrivance one can use a fine and powerful jet 

 of water, which will effectually wash away all the fine dust left behind 

 by the dry brush. This plan is vastly better than treating the fossil 

 with dilute hydrochloric acid, the use of which should be limited to 

 the Flamborough Head sponges, the oxide of iron sponges of the 

 Upper and Middle Chalk, and the bulky lithistids and hexactinellids 

 of the Chalk-marl. Even in the case of these it should be employed 

 with great caution, and then only in a very weak form. 



Now, a few words as to the choice of knives. The ordinary 

 dissecting scalpel is the best type of knife for most of the work, and 

 in the field there is nothing better than the Swedish knife. But any- 

 one who has cut up much chalk will have a lively recollection of the 

 soreness of the middle joint of the index finger, due to the pressure by 

 the back of the knife. This led me to devise the round-ended knives 

 with a cutting surface extending from the front edge to half an inch 

 down the back. The ease and rapidity with which one can with 

 such a knife work off masses of chalk has to be seen to be believed, 

 for by pushing the broad, round, cutting point one obtains all the 

 power of the action of a chisel, with all the delicacy of finger manipu- 

 lation. Further, one can be sure of not puncturing or scratching the 

 fossil as one does with a sharp pointed knife, which as often as not 

 breaks off as soon as any pressure is employed. One of the chief uses 

 of these round-ended knives is to be found in working out the Plocos- 

 cyphiae of the white Chalk, for the matrix can be scooped out of the 

 chambers without damage to knife or specimen. 



That beautiful work can be done with an ordinary knife and 

 tooth-brush a visit to the Natural History Museum or School of 

 Mines will abundantly prove. Even in private collections one some- 

 times sees beautiful results, and in none is this better shown than in 

 the cabinets of Mr. James Fox, of Stamford Hill. But excellent as 

 are these results, one cannot but deplore the great amount of time 

 expended, especially when far more accurate and complicated work 

 can be done in a tenth part of the time. It is the American dental- 

 engine which has worked this revolution. 



The engine has been employed by me for more than three years, 

 and as fresh ideas have been evolved, so has the degree of mechanical 

 perfection in the work increased. The use of the dental-engine was 

 suggested while working at a fine Cidaris sceptvifeva, for it was easy 



