^ Dr. WoLL ASTON on the elementary Particles 



or less obtuse according to the degree of oblateness of the 

 primitive spheroid. 



It is at least possible that carbonate of lime and other sub- 

 stances, of which the forms are derived from regular rhom- 

 boids as their primitive form, may, in fact, consist of oblate 

 spheroids. as elementary particles. 



It deserves to be. remarked, that the conjecture to which we 

 are thus led by a natural transition, from consideration of the 

 most simple form of crystals, was long since entertained by 

 HuYGHENS,* when treating of the oblique refraction of Iceland 

 spar, whkh he so skilfully analysed. The pecuhar law ob- 

 servable in the refraction of light by that crystal, he found 

 might be explained on the supposition of spheroidical undula- 

 tions propagated through the substance of the spar, and these 

 he thought might perhaps.be owing to a spheroidical form of 

 its particles, to which the disposition to split into the rhomboidal 

 form might also be ascribed. 



By some oversight, however, the proportion of the axes of 

 such an elementary spheroid is erroneously stated to be i to 

 ^ ; but this is probably an error of the: press, instead of i to 

 =«,8, for I find the proportion, to i be nearly X: to ^i^y. In fig. 

 «15, Fis the apex of a tetrahedron cut from !an acute rhomboid 

 similar to fluor spar,' and: the sections of two > spheres are re- 

 presented round the centres: Rand C. I isithe. apex of a cor- 

 responding portion xsut; from the sumnpiit of a rhomboid of 

 Iceland spar^ as composed of spheroids having the same dia- 

 ineter as the spheres. In the former, the inclination FCT of 

 the edge of the tetrahedron to its base is 54° 44,'; in the latter, 

 ■ he inclination ICT is 26*. 15' ; and the .altitudes FT, IT are as 



• HuvcHEKii Op. R«Uq. Torn* I. ^TsMt^de Luminc^ p. 70. 



