2(50 Professor Delesse on the 



seem a justifiable supposition that the velocity of the propagation 

 of electricity is dependent on the nature as well as on the dimensions 

 of the medium. In the voltaic circuit bad conductors become more 

 heated than good conductors, and electric discharges are very 

 variously complicated phenomena, as appears by the latest experi- 

 ments of Riess. The now prevailing views respecting what is com- 

 monly called " connection through the earth " are opposed to the 

 view of linear molecular conduction between the two ends of the 

 wire, and to the conjectures of impediments to conduction, and of 

 accumulation and discharges in a current ; as that which was once 

 regarded as intermediate conduction in the earth is now supposed to 

 belong only to an equalisation or to a restoration of electric tension. 



Although, according to the present limits of exactness in this kind 

 of observation, it is probable that the aberration constant, and there- 

 fore the velocity of light, of all the fixed stars, is the same, yet the 

 possibility has more than once been spoken of, that there may be 

 luminous bodies in space whose light does not reach us because, from 

 their enormous mass gravitation constrains the luminous particles 

 to return. The emission theory gives to such fancies a scientific 

 form : I only allude to them here, because I shall subsequently have 

 to notice certain peculiarities of motion ascribed to the star Procyon, 

 which appear to point to a perturbation by dark bodies. It is the 

 object of this part of my work to touch on matters which, during 

 the time in which it has been in progress, have influenced the direc- 

 tion which science has pursued, and thus to mark the individual 

 character of the epoch in regard to the study of nature, whether in 

 the sidereal or the telluric sphere. — Sabine's Edition of HumhoMfs 

 Cosmos. Vol. iii., Part 1, p. 71. 



On the Rose- Coloured Syenite of Egypt. By Professor 

 Delesse, Engineer of Mines. Copy communicated by the 

 Author. 



The rose-coloured syenite of Egypt is formed of quartz, 

 orthose, oligoclase, mica, and frequently also of hornblende.* 



The quartz is translucent and grey ; it has sometimes a 

 slight violet or smoky tint, arising, as in the quartz of pro- 

 togine, from the possible presence of a small quantity of 

 organic matter. 



The orthose is of a pretty pure rose-colour, and reminds 

 one of that of the orthose of the syenite of the Vosges, 



* See also Lieut. Newbold on the Geology of Egypt, Quart. Journ. Geol. 

 See. 1848, vol. iv., p. 340. 



