92 Scientific Intelligence. 



Paris is quickly sifted in, with constant stirring, until the mass 

 becomes of the proper density. 



(3) The liquid mass is now poured rapidly without the forma- 

 tion of any bubbles upon the surface of the glass on the table, 

 filling all the space between the strips of wood. .Then as quickly 

 as possible, the other plate of glass is put over the liquid, great 

 care being taken that no bubbles creep in, and then heavy 

 weights are put on this glass, pressing out all excess of liquid 

 plaster. In the course of fifteen or twenty minutes, depending 

 on conditions not yet thoroughly understood, the upper glass can 

 be separated from the plaque, by gradual lifting at one side. 



In ten or fifteen minutes more, the plaque can be separated 

 from the floor glass. At this time, a small hole is to be made in 

 one corner, about an inch and a half from the edge; this serves 

 for hanging the plaque on a nail in a dry room. The drying 

 takes place slowly in winter, but in summer the whole sheet 

 will be thoroughly dry in a few days. 



The plate can now be cut into any desired shape and size by a 

 simple device. First, make a deep scratch in the plaster where 

 the break is desired, and then break exactly as a square of glass 

 is cut. When the break has been made, the edge is finished by 

 means of a plane, and it can be bevelled also, if necessary. 



If the surface has too glossy a finish, reduce the luster by a 

 common stiff brush carried evenly over the whole surface. 



We have made many attempts to improve the color of the 

 plaques by the addition of various fine pigments, but the effect 

 has always been unsatisfactory. The color tints with a little 

 Prussian-blue, and the warmer tints with a very little vermillion, 

 were liked by many, but as a rule, the plain un dazzling white 

 has been found best. 



We are now employing plaques of this sort also for our cases 

 in which we are installing specimens of seeds, fruits, etc., which 

 are better exhibited without any covering at all. In this way, 

 for instance, specimens illustrating dissemination are placed 

 before the public in a very attractive manner. The contrast 

 between the specimen and the pure white plaster mount is in no 

 instance unpleasing. 



Cambridge, June, 1906. 



2. The American Association for the Advancement of Science. 

 — The special summer meeting of the American Association will 

 be held in Ithaca, New York, from June 28th to July 3d. Sev- 

 eral Societies, including the American Physical Society and the 

 American Chemical Society, are to meet at the same time in 

 affiliation with the Association. Professor William H. Welch, 

 of Baltimore, is the President of the Association for the Ithaca 

 meeting, and the Vice Presidents of the several sections are 

 given in the following list: Section A, Mathematics and Astron- 

 omy: Edward Kasner, Columbia University ; B, Physics: W. C. 

 Sabine, Harvard University ; C, Chemistry : Clifford Richard- 

 son, New York City ; D, Mechanical Science and Engineering : 

 W. R. Warner, Cleveland ; E, Geology and Geography : A. C. 



