_ sible that all four may have a similar constitution as is sh 
In the following table, and the important class of minerals 
a s Which spi . i» 
J. P. Cooke, Jr., on Atomic Ratio. 389 
Feldspars. 
Triclinic, ym, [Al |"NO, ae 
be [Na,, Ca], [Al,]""4O,"48i,0, 
Isometric K,, [Alo [""'O, aa 
vili viiiQ; 
1, 0,"18i,0, 
Triclinic,,  [Ca, Na, }, [Al |""0,""'Si,0, 
6 ; oe A Py ee z 
Monoclinic, Ko, Ale!” Us Oe 
Clays. 
Orthorhombic, H,, [Al ["'0,""8i.. BO 
assive, 
Orthorhombic, H,, [Al, |"'O,"''Si,0, 
Massive, H,, f Al, |?" OL" "8i,0, 
Zeolites. 
Orthorhombic, [Na,,Ca], [Al, ]“'0,""Si,. 25H,O 
“3 Na,, ie EO 40s. tHaV 
Monoclinic, Ca, | Al, ["'O,""'Si,0,. 3H,0 
Isometric, Na,, [Al, @"'0,""81,0,. 2H,0 ' 
Ca, [Al, “"%0,""'Si,0,. 6H,0 
exagonal, 
Orthorhombic, Ba, | Al, |""0,""Si,O,. 5H,0 
Monoclinic, Ca, Fal? in gieoe, 5H,0 
Orthorhombic, Ca, [Alp ]""O,"4Si,0,. 6H,0 
And it will be seen that the atomic ratio of the basic radicals 
to the various complex acid radicals is the same for all these’ 
minerals, although the ratios of the basic radicals to the silicon 
alone are quite different. The last, however, vary according to a 
Simple law and indicate a still further relation between the seve- 
tal species, These relations may be discovered by a simple 
Mspection of the symbols, but they will be rendered much more 
Striking by tabulating the atomic ratios deduced as above. ae 
Lastly, the atomic ratios express the results of analysis in 
the simplest possible terms and in a form, in which they can be s 
Most readily compared in various combinations, and such com- — 
ations bring out unexpected results. Thus the atomic ratio 
of zircon Zr: 0 ,: Si(4:4) is the same as that of garnet, when 
the sum of all the basic radicals is compared with the sili- 
Con, and the two minerals although belonging to different sys- 
tems have nevertheless very nearly the same crystalline form. 
Again, zircon is isomorphous with tin-stone and rutile. Now 
the total quantivalence of all the radicals both basic and acid 
in each of these minerals (taking the symbols as they are usually 
q _ Written) is a multiple of four and there are reasons for believing 
. that the molecules of the three, last named, are more cond 
n the common symbols would indicate. It is therefore pos- 
inel is the type may be included in the same scl 
