PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 671 



crystallize diamonds of any value. It may be thot the crystalliza- 

 tion of diamonds of large size is a work of time — such work as 

 only nature can accomplish in a satisfactory way. No doubt 

 fluorine, or some similar element, has played a part in the produc- 

 tion of the diamond. It is a suggestion worthy of attention. 

 Compounds of that element are very imperfectly known at pres- 

 ent. In chemical works, at different times, processes are described 

 whereby carbon has been separated from combination, and, obtained 

 in a 'crystallized form; but all these statements, he believed, were 

 entirely erroneous. Liebig has a notion that diamond is the result 

 of the final natural decay of vegetable matter; but in nature wo 

 do not find diamonds under those conditions where we observe the 

 final products of natural decay — in our coal-fields, for example, an- 

 thracite is one of the final results of this decay; and no one, he be- 

 lieved, had ever found diamond in a coal-field, where one ought 

 to find it, if it is the result of this final decay. We find graphite 

 in nature, which is a crystalline form of carbon, just where we 

 should expect to find it, but we do not find the diamond there. 



Metallic Tree. 

 Dr. Vanderweyde alluded to the fourth item read, and described 

 a tree he had recently seen, fourteen inches high, formed of iron 

 filings, at the manufactory of Mr. T. N. Hickcox, in John street, 

 New York. The filings fell in such regular order so as to form a 

 tree. The iron becoming magnetic caused them to hold to each 

 other. 



Calculating Tables. 



Mr, J. Johnson exhibited a set of calcuhiting and multiplying 

 rotary cards for teaching children to add, multiply, and divide 

 figures expeditiously. 



Prof. Grimes remarked that Mr. Byington, a teacher of a school 

 at Cold, Spring, N. Y., had a system of teaching addition by a sort 

 of mnemonics. He had seen quite a large number of figures added 

 up in ten seconds. Mr. Byington's method was to accustom the 

 pupils to look upon two or more figures as a whole — such as 8 and 

 8 are sixteen. By a little practice, several figures are intuitively 

 associated together at a glance, and rapid calculation theiieby much 

 facilitated. 



Plastic Anatomy. 



Mr. Julieu Ledion said he had the honor to call the attention of 

 the Polytechnic Association to his specimen of pathological anato- 



