592 



SCIENCE. 



[N. S. Vol. XXV. No. 641 



attempting to solve this problem quite a num- 

 ber of substances have been tried by the 

 writer, such as plaster, gntta percha, wax, 

 modeling clay, etc., and when the relief is not 

 great and other conditions are favorable, some 

 acceptable impressions have been made. In 

 many cases, however, the shape of the mold is 

 such that the opening, through which the cast 

 must be drawn, is too small to allow it to pass, 

 if the above substances are used, or the sculp- 

 turing, on the plates of a crinoid, for instance, 

 is so delicate that in drawing a rigid cast out 

 of a rigid mold, the finer markings are de- 

 stroyed. 



The properties which a substance must 

 possess to give a reproduction of the form 

 of a shell over which a natural mold was 

 formed are: (a) ability to become liquid or 

 plastic to such a degree that it can be forced 

 into every crevice of the mold; (&) little or 

 no shrinkage in cooling or drying; (c) elas- 

 ticity, to insure its resuming its original form 

 after the distortion necessary in drawing the 

 cast out of the mold and (d) durability. Glue 

 possesses most of these properties and gives 

 satisfactory easts for some purposes, but they 

 shrink after a day or two. A substance found 

 very satisfactory when the molds are large 

 and the ornamentation not too delicate is the 

 so-called ' roller composition,' such as is used 

 in making the ink rollers on printing presses. 

 This composition, which can be purchased at 

 any printers' supply house, is used as follows : 

 Melt the composition in a double glue pot, to 

 avoid burning, as a comparatively high 

 temperature is needed. Heat the natural 

 molds as hot as they can be handled and 

 thoroughly oil with lard oil just before the 

 composition is put in. Keep the mold hot for 

 five or ten minutes after the composition is 

 put in and stir the composition to allow any 

 air bubbles to rise to the top, otherwise the 

 mold may not entirely fill. After the com- 

 position is quite cold it can be removed from 

 the mold and will last for a long time without 

 shrinking. The writer has some casts that 

 were made in 1901 from this substance and 

 they are still in good condition. 



When the molds are small and irregular 

 with delicate sculpturing, the writer was un- 



able to get rid of the bubbles or to obtain 

 sharp impressions with the composition. Un- 

 vulcanized rubber, such as is used for making 

 rubber stamps, was tried and by vulcanizing 

 it in the molds, under pressure, very satis- 

 factory casts have been made on which tha 

 surface markings are perfectly preserved. 

 The process is as follows : Dust the inside of 

 the mold and anything that is to come in 

 contact with the rubber with talcum powder 

 to prevent sticking. Cut the rubber in small 

 pieces and, after cleaning in benzine, pack it 

 tightly into the mold, until the mold is a 

 little more than fuU; then put the mold in a 

 screw clamp to press the rubber while it 

 is vulcanizing and insure complete contact 

 throughout the mold. The vulcanizing is ac- 

 complished by placing the mold in a drying 

 oven heated to 135° or 140° Centigrade. The 

 time required varies from half an hour to an 

 hour or more according to the size of the 

 mold. 



Arthur W. Slooom 

 Field Museum of Natubal Histoky 



PIERRE EUGENE MAROELLIN BERTHELOP 



France, for the third time in the space of a 

 few months, moxirns the loss of an illustrious 

 savant. Again the nations of the world ex- 

 tend their sympathy. The heroes acclaimed 

 were not martial victors over mankind, whose 

 honors were bought in the price of blood, but 

 men of lofty ideals who conquered nature, 

 brought truth to light, instituted new indus- 

 tries and improved old ones, thus bettering 

 man's physical, and through enlightened 

 thought elevating his moral condition. Truly 

 ' science guides humanity.' 



Curie, Moissan, Berthelot ! How varied the 

 achievements of each, though each chose chem- 

 istry as a field of labor. How differently each 

 worked out his task and how successfully. 



Berthelot was born in Paris, October 25, 

 1827. His father was a physician, and the 

 young man inherited not only a taste for a sci- 

 entific career, but was schooled most effectually 

 for it. His education at the Lycee Henri IV. 

 developed the taste for historical research 



'Read at the meeting of the New York Section 

 of the American Chemical Society, April 5, 1907. 



