COLLECTING AND PREPARING. 809 



tion of parts of the fossil. A number of engraver's tools will be 

 found useful for scraping away small masses of matrix. A pointed 

 steel pen in a holder, with one half side broken away makes a very 

 good tool for fine work. In working on limestone with this tool, 

 always keep the specimen wet, or even under water. In this case 

 a white enameled dish should be used, and the specimen laid on a 

 piece of rubber on the bottom. A pair of wire nippers, with the 

 cutting edge at right angles to the longer axis of the tool will be 

 found most serviceable. With a little dexterity gained through 

 practice, specimens may often be cleaned by use of this tool alone. 



Good stiff brushes — tooth brushes, nail brushes and wire brushes 

 are very serviceable tools in cleaning fossils. 



Various mechanical devices may be employed to advantage in 

 some cases. Such is the dental engine in which brushes are fixed 

 and rapidly revolved in contact with the dry matrix. When the 

 fossil is harder than the matrix this works well. The sand blast 

 has also been used for this purpose. Freeing specimens from the 

 matrix by an artificial freezing mixture has also been employed. 

 A porous matrix saturated with a hot solution of sulphate of 

 magnesia, or other rapidly crystallizing salt will, on cooling, be 

 loosened by this crystallization, and may be removed by brushing. 

 Care should be taken that only the matrix is saturated and this can 

 be accomplished by applying the hot solution with a brush. 



Separation of fossils from a shale matrix is often accomplished 

 by the use of caustic potash. Small discs cut from a stick of 

 potash, are placed on the shale particles to be removed, and are left 

 there over night. The action may be started by adding a drop of 

 water. In the morning the shale will be found in a disintegrated 

 state, — and may be washed away. It is however important that 

 the specimen should be thoroughly washed in pure water to which 

 a drop of hydrochloric acid may be added. Otherwise a white 

 efflorescence will appear and the fossil may become disintegrated."* 

 Pyrite nodules carrying fossils, may be broken by heating them and 

 then plunging in cold water.- 



^ For an explanation of this process, see E. Bose and Victor V. Vigier, Central- 

 blatt fiir Mineralogie, 1907, pp. 305-313. 



^ For the application of this process and the results, see F. B. Loomis, Bull. N. 

 Y. State Museum, LXXIX., pp. 892-920, 1240-1248, 1903. 



