186 ANNUAL OF SCIENTIFIC DISCOVERT. 



nized groups, and at the same time indicates new symmetries 

 and new groupings. Prof. Seely believes that no diagram of 

 elasjiilication of the ek'nients has ever been devised which is so 

 simple and so comprehensive. The paper continues by pointing 

 out the importance and the consequences of the fact of the pair- 

 ins: of the elements. It is a new conlirmation of the doctrine of 

 atomicity and of the truth of the atomic numbers. It indicates 

 the probability that very few more elements are to be discovered, 

 and assists in bringing chemical phenomena into the domain of 

 mathematics and ordinary physics. 



HEAT. 



M. Le Roux has made some experiments with the vapor of 

 sodium, and examined its capability or incapability of passing 

 through rock salt. Two crucibles of rock salt were prepared, a 

 thin plate of the same substance placed between them, and in one 

 of the cavities sodium was placed. Notwithstanding a bright red 

 heat maintained lor several hours, the piece which was not in di- 

 rect contact with the sodium vapor remained completely unal- 

 tered, even where it had been in contact with the plate already 

 completely penetrated. Chloride of sodium is not attacked by 

 the vapor of sodium, but soda corrodes it energetically. A very 

 small quantity of soda suffices to hermetically seal two surfaces 

 of rock salt, sodium preserving its lustre for several months in a 

 crucible of this kind. Potassium vapor does not attack its chlo- 

 ride, but it covers the chloride with a bright blue substance, in 

 which, possibly, chemists recognize the suboxide of potassium. 



Mr. W. P. Dexter has described a new gas-lamp for heating 

 crucibles, etc. The ordinary Bunsen burner is known to act upon 

 the surface of platinum vessels brought into contact with the 

 inner line of the liiune ; the metal loses its polish, becoming su- 

 perficially porous and spongy, and requires the use of the burn- 

 isher to bring it back to its original state. This alteration of the 

 surface is attended with a change of weight, and Mr. Dexter has 

 consequently devised the following arrangement: He removes 

 the air-tube of a common Bunsen lamp, and puts in its place a 

 somewhat longer one of glass or iron, of about 12 millimetres in- 

 ternal diameter. The gas-jet has a single circular aperture, and 

 should be in proper proportion to the diameter of the tube, which 

 may be held in any of the ordinary clamped supports. The tube 

 being raised sufliciently above the jet to allow free entrance of 

 air, and a full stream of gas let on, a " roaring '' flame is proiluced, 

 of which the interior blue cone is pointed, sharply delined, and 

 extends only about half an inch from the top of the tube. A pol- 

 ished platinum surface is not acted upon by this flame, provid(;d 

 it be not brought into contact with the interior cone. In the 

 Bunsen burner, as usually made, the supply of air depends upon 

 the diameter of the tube, the holes at its l)ase being more than 

 suflieient to supply the draught. With the wider tube, it is 

 necessary to limit the admission of air by depressing the tube 



