406 Scientific Intelligence Geology. 



Then if H denote the vertical line from B to the plane of the 

 stratum passing through A, we have 



H = h+d (tan D. cos I); 

 or H = d (cot E + tan D. cos I), . . (1.) 

 If t denote the perpendicular thickness of a bed of the same 

 stratified rock, so that the parallel plains passing through A and 

 B are on the opposite sides of the seam, or stratum ; then 

 t H cos D = d (cos D cot E + tan D cos I) 

 or t - d (cos D cot E + sin D cos I). . . (2) 

 When t = o, that is, when A and B are in the same plane of 

 a face of the stratum, the formula (2) may be expressed entire- 

 ly in circular functions, and becomes 



cot E cos D = sin D cos I 

 or cot E = tan D. cos I . . . (3) 

 This expression may be applied to determine whether two 

 points, in a disjoined stratified rock, of the same character, be- 

 long to the same layer of the bed, when these points are separat- 

 ed by an extensive ravine or valley. The expression (1) may 

 be of considerable use to miners and practical engineers. 



23. Analysis of Steatite and Algalmatolite. Mr Lychnell 

 communicates in PoggendorPs Journal, B. xxxviii. the following 

 analysis of steatite or soap-stone. I. From Caunegou : Silica, 

 66.70; magnesia, 34.23 ; oxide of iron, 2.41 ; =99-34. II. From 

 Sala : Silica, 63.13 ; magnesia, 34.30 ; oxide of iron, 2.27 ; 

 = 99.70. III. From Scotland: Silica, 64.53; magnesia, 27.70; 

 oxide of iron, 6.85 = 99.08. IV. From China : Silica, 66.53 ; 

 magnesia, 33.42 ; oxide of iron, a trace; = 99-98. V. From Bay- 

 reuth : Silica, 65.64 ; magnesia, 30.80 ; oxide of iron, 3.61 ; 

 = 100.05. Mr Lychnell also communicates the following analysis 

 of algalmatolite : Silica, 72.10 ; alumina, 24.54 ; oxide of iron. 

 2.85 ; trace of magnesia. 



24. Analysis of Radiated Zinc-Blende. Mr Lowe, in Pog- 

 gendorf, gives the following analysis of radiated blende : Sul- 

 phur, 32.75 ; cadmium, 1.78 ; iron, 2.20 ; zinc, 62.62 ;= 99.35. 



25. Analysis ofPlagionite. Lead, 40.98 ; antimony, 37.53 ; 

 sulphur, 21.19 ; = 100.00. It results from this analysis that the 

 plagionite is a peculiar chemical compound. Kudernatsch in 

 Poggendorf, B. xxxvii. 



