NATURAL PHILOSOPHY. 155 



degrees, oi', better still, according to the latest improvements of 

 M. Abaddie, with the altitudes corresponding to the tempei-atures, 

 supposing them to be the boiling points of water. The hypso- 

 meter is, for several reasons, more suitable for the purposes of 

 travellers than the barometer: it is more easily carried, and less 

 easil)^ injured, and it requires, not an observation, but an experi- 

 ment which is made with greater facility, and is less subject to 

 error. — Intellectual Observer, October, 186G. 



THERMO-ELECTRIC ELEMENTS OF GREAT MOTIVE POWER. 



^ Stefan has examined a variety of mineral substances, with rela- 

 tion to their thermo-electric power at high temperatures. The 

 mineral to be examined was placed upon one end of a strip of 

 copper, Avhile the end of a copper wire rested upon the minei-al, 

 the whole being pressed together to insure contact. The wire and 

 copper strip were connected with a galvanometer of gi-eat resist- 

 ance, and the copper strip was then heated by a spirit lamp. In 

 examining the mutual relations of the minerals, a copper strip was 

 placed between them, wires attached to the free ends of the frag- 

 ments of mineral, and the whole pressed together by a wooden 

 press. The free end of the copper stinp was then heated, and the 

 heat conducted to the minerals. In the following enumeration of 

 the elements employed, the positive element is always placed first ; 

 and the number apjjended signifies how many of the elements give 

 an electro-motive force equal to DanieU's cell : — 



1. Foliated copper pyrites — copper; 26. 



2. Compact copper pyrites — copper; 9. 



3. Pyrolusito — copper; 13. 



4. Compact copper pyrites — foliated copper pyrites; 14. 



5. Copper — crystallized cobalt pyrites; 26. 



6. Granular cobalt pyrites — copper; 78. 



7. Copper — iron pyrites; 15.7. 



8. Compact copper pyrites — iron pyrites; 6. 



9. Foliated copper pyrites — iron pyrites; 9.8. 



10. Copper — erubeseite; 14. 



11. Fine bleischweif — copper; 9.8. 



12. Coarse bleischweif — copper; 9. 



13. Galena in large crystals — copper; 9.8. 



14. Bleischweif — erubeseite; 5.5. 



The great influence of stnicture upon the thermo-electric rela- 

 tions is seen in Nos. 1, 2, and 4, and still more in 5 and 6. A mass 

 of cubical crystals of galena was at some points negative, at oth- 

 ers positive, to copper. The densest. No. 14, has the greatest 

 electro-motive force yet observed in thermo-electric series ; but 

 the substances employed are all bad conductors. The author con- 

 siders, and we think justly, the above results as of great import- 

 ance for the physics of the earth, and proposes to continue the sub- 

 ject. In a note to vStefan's paper, Poggendortt" calls attention to 

 an observation of Marliach, made in 1857, according to which, 

 crystals of iron pyrites (Fe. S2) and ofcobaltine (Co. S2 — Co. Aso), 

 which cannot be distinguished, either in crystalline form or in 



