220 The American Geologist. Marcii,i897 
the conglomerate. This is in support of the view everywhere exprepsed 
in the article that phosphate is a littoral formation. 
2. On c]i(tlcedoiit/ j>ebblea 'in glauconite lhneHtone--Conglonierate at 
Sollcroii. The interest in these chalcedony pebbles rests on the fact 
that some of them contain micro-organisms, among which some are 
like foraminifera, others resemble bryozoans, etc., but the commonest 
are spicules of siliceous sponges: of the nature of these there is no ques- 
tion [figures are given of these, they are mostly hexactins]. Some of the 
fossil.^! found he says are with certainty to be referred to Monadites.* 
Herr Hedstrom appears to think that these chalcedony nodules did not 
originate in the bed where they are found, but have been derived from 
an older formation [Cambrian?] by erosion. 
3. On the occurence of phoaphatic concretions in recent sediments. 
In this is discussed the distinctions between shore deposits, shallow sea 
deposits and deep sea deposits; with many references to the work of the 
Challenger expedition, and of the depths at which phosphate bearing 
sediment had been met with. 
4. On the prohable origin and building up of pliosphatic layers. 
The most common opinion on this point is that the mineral phosphate 
of lime is derived from organisms that secrete phosphorus. At the 
present time it may be derived from the bones of animals living on the 
land, or from the excrement of birds: or may be formed from marine 
organism, as bones of fishes, shells of crustaceans and brachiopods. 
Sea water now operates on similar remains rich in phosphorus more or 
less directly, so' that the phosphoric acid is released and combines with 
iron or lime in the water. This material forms adhesive gelatinous 
drops, which have the same qualities as colloid bodies, namely to stick 
together and form concretions. Somewhat analogous (to the mode of 
growth of phosphate nodules as described by Dr. John Murray in the 
Challenger report on deep sea deposits) seems to be the mode of accum- 
ulation of the chalcedony nodules in the green limestone conglomei'ate 
of Dalarnia (described above); although the condition there has been 
yet more favorable because hydrated silica is even more a colloid body. 
After describing two methods by which phosphate nodules are pro- 
duced, viz: the accumulation in a colloid form, and the replacing of 
carbonic acid in lime by phosphoric acid, Herr Hedstrom jjroceeds to 
speak of various sources of phosphates in later formations, and at the 
present time, and finally decides upon the shells of Inarticulate Brach- 
iopoda as the chief source of phos^jhatic deposit in the early Cambrian. 
He gives many quotations from authors who have written on the sub- 
ject of phosphate rocks, both of past geological ages and of the present 
time. Herr Hedstrom claims that all the original geological marine 
phosphate deposit have been formed in the littoral zone, giving the fol- 
lowing reasons: (a) They occur with coarse sediment, conglomerate, 
gravel and sand, (b) That phenomena sometimes accompany the de- 
* In this connection he quotes W. D. Matthew — On phosphate nodules from the 
Cambrian of southern New Brunswick. Trans. N. Yorl< Acad. Sci. vol. XII, 1892-3, 
p. 112-114, who also describes chalcedony nodules p. 108. 
