i8 9 4-95-] x 99 



than the mean of the four, and more than io°/ lower than the 

 least of these, the ferric oxide though higher than the lowest is 

 still more than 4°/ o less than the mean, the potash is nearly 

 double the highest given in the four, while the water is some- 

 where about the mean. One great difference observable is in 

 the ferrous oxide, where against a maximum of i'95°/ ^ n tne 

 marine Glauconite the Woodburn sample shows i6*8i°/ . To 

 turn now to Table 2. This is a resume of twelve analyses of 

 Glauconite from rocks which have been selected by Professor 

 Cole as fairly similar to ours, and which are published in the 

 " Handbach der Mineralogie " by Dr. C. Hintze for 1892. 

 Here, again, though we might fairly expect a closer correspon- 

 dence with our own than in the case of the marine Glauconite, 

 we find in comparing them with each other and with our 

 Woodburn mineral the same discrepancies in nearly every 

 particular — the silica varying from 58°/ to a little over 43°/ e , 

 which, however, is still somewhat higher than ours, the ferric 

 oxide varying from 32'8°/ to (in three analyses) nil, our figure 

 coming close to the mean ; and, in fact, a glance will show that 

 these differences obtain throughout, so that the average result 

 is really useless as a standard. It will be noticed that the 

 ferrous oxide which is so low in the marine Glauconite of Table 

 1 gives us in Table 2 figures much more nearly agreeing with 

 the Woodburn Glauconite, the rocks being similar in this case. 

 The one point which does seem to come out clearly in this 

 comparison is the relative poverty in silica of the Woodburn 

 specimen, though even that is not much below the lowest in 

 Table 2. In this connection it is worth noting that in Table 1 

 the silica is lowest and the potash highest in these cases in which 

 the green, and especially the dark green, casts predominate, 

 casts agreeing in appearance with those composing the whole 

 of our Woodburn specimen. Whether this is merely a coinci- 

 dence in a particular case or has a definite significance is not 

 certain. The fact that where the dark green casts are most 

 numerous the mineral particles and silicious organisms are few 

 probably accounts for the variation in silica to a large extent, 



