Classification.

In the present state of knowledge regarding the anatomy of fossil, and living, palms the investigator may well adopt the system used by Stenzel (3) which is the result of the most extensive study of the anatomy of fossil palms yet published. Like all artificial systems it presents some difficulties in application. For example, when the writer described P. anchorus he was inclined to place it in Stenzel's class C, "Kokos-like stems," because no marked difference in size, shape or arrangement of the inner and outer bundles was detected. The bundles in this species are, however, much too far apart to agree with the "Kokos-like stems." Again, P. anchorus might well be placed in the subdivision Lacunosa of Stenzel's group Complanata, which includes species with the fibrovascular bundles separated from one another by more than one diameter. But so doing involves the assumption that in the extreme outer portion of the stem, lacking in the specimen, the fibrovascular bundles were close together, this being a distinguishing character of Stenzel's Class B. "Corypha-like stems."

The two species considered here fit easily into Stenzel's scheme. In P. cheyennense both peripheral and more central bundles have the sclerenchyma portion much larger than the vascular portion, which together with the fact that the central bundles are more widely separated than the peripheral places it among the "Corypha-like stems." The shape of the sclerenchyma portion, which is flattened where it joins the vascular portion, places it in Group IV, "Complanata," and the close arrangement of its fibrovascular bundles and its dense fundamental tissue indicate that it belongs to the sub-group "Solida.

P. cannoni also apparently belongs to the group "Complanata" but to the sub-group "Lacunosa" because the fibrovascular bundles are more than one diameter apart, and the fundamental tissue has large intercellular spaces. Among species belonging to this sub-group it most nearly resembles P. remotum in the arrangement of its fibrovascular bundles and in the presence of thick walled cells scattered among the cells of the fundamental tissue. The vascular portion of the bundle in P. remotum is, however, much larger as compared to the sclerenchyma portion, than in P. cannoni.

Bureau of Plant Industry,
Washington, D. C.

ART. XXXII.-The Isomorphic Relations of the Sulphosalts of Lead and Copper; by WILLIAM F. FOSHAG.1

The sulphosalt minerals are chiefly compounds of lead, silver and copper with sulphur and antimony, arsenic and bismuth. Rarely iron, zinc, mercury, thallium and manganese enter into the composition of these minerals to any considerable extent, while selenium and tellurium may replace some of the sulphur. In these compounds sulphur, selenium and tellurium are strictly isomorphous, as are also antimony, arsenic and bismuth. A critical survey of all reliable data, however, indicates that the lead, and silver and copper are not isomorphous and that the formation of mixed crystals does not take place. This fact does not seem to have been generally recognized and our standard text-books contain formulas of the type (Pb,Ag2),Sb,S11 (diaphorite) and (Cu,Pb)3Sb2S ̧ (bournonite). We find, where the analyses are reliable, that the silver minerals, pyrargyrite, stephanite, etc., are remarkably free of lead and that the lead minerals rathite, sartorite, etc. are free of copper and silver. H. Rose was the first to state this fact. He says, "I have never seen lead sulphide occurring together with the other metallic sulphides except copper sulphide and sometimes with iron sulphide, which, however, are in such small amounts that they do not appear to belong to the compound. The compounds that do not contain lead sulphide are completely free of lead even when they are surrounded by galena or the crystals rest upon galena.

These deductions of Rose seem to have received little attention other than occasional denial in the early literature. We shall see that his generalization is correct except for a certain type of compound.

In order to determine whether there is considerable miscibility between lead on the one hand and silver and copper on the other the writer undertook to collect a number of analyses of the sulphosalts, noting the kind of material upon which the analyses were made. Unfortunately the descriptions of the material analyzed were in

Published by permission of the Director of the Smithsonian Institution. Ueber die in der Natur vorkommenden nicht oxvdirten Verbindungen des Antimons und des Arseniks, Pogg. Ann., 15, p. 469.

almost all cases hardly adequate to determine how free of admixture the particular sample was. Only in a few cases were any mineralographic examinations attempted and these invariably showed small amounts of admixture even where crystals were used. In many cases copper and silver have not been determined in lead salts or lead sought for in copper or silver salts. The sums, however, indicate that their amounts, if present at all, are negligible. Because of this unsatisfactory character of the analyses they are not included here and only the general results will be noted. Of 32 analyses of lead minerals, made mainly upon crystallized material and embracing all the species, none showed a copper or silver content of over 1 percent and in most cases hardly more that 0.5 percent. Of 21 copper salts only one showed a percentage of more than 1 percent of lead. Of the silver salts two analyses from the same locality made upon "excellent" material showed over 1 percent of lead. Twenty-three showed less than 1 percent or none at all. These analyses were picked only to the extent that the material was crystallized or apparently homogenous as far as determinable.

It is evident that the miscibility between lead on the one hand and silver and copper on the other is very slight if it takes place at all. It is difficult to determine from the existing analyses whether the small amounts of lead, or of the silver and copper, are due to slight miscibility or to admixture. Since mineralographic examination has shown the presence of foreign material even in the best crystallized samples it is safe to assume that the small percent of these constituents are foreign to the mineral proper.

We have another type of compound in which lead, silver and copper do occur together in considerable amounts. These include such minerals as diaphorite, bournonite, freieslebenite, etc. A survey of the analyses of these minerals shows them to have a remarkably constant composition. They are in fact double salts. In some cases the minerals have been recognized as double salts, in some this has been suggested, but in a large number of cases they are regarded as isomorphous mixtures. In all cases the ratios of the constituent sulphides to each other are simple and definite. These minerals are as follows:

AM. JOUR. SCI.-FIFTH SERIES, VOL. I, No. 5.-MAY, 1921.

The above formulas show the simple ratios of the constituent sulphides. This, together with the constancy of composition, even in specimens from widely differing localities and occurrences, places these minerals definitely as double salts.

There are no simple silver analogues of the lead salts. Where a silver-bearing mineral falls into a group with a number of lead minerals it is one of the double compounds given above. In the case of the copper salts there are a few cases in which they are similar to the lead salts in type of compound but there seems to be evidence that they also are not isomorphous.

The conclusions arrived at from a critical survey of the best analytical data are: (1) that lead on the one hand and silver and copper on the other hand are not isomorphous and that they do not form mixed crystals; (2) that the silver-lead or the copper-lead sulphosalts are double salts.

3 See Wherry and Foshag, A new Classification of the sulfo-salt Minerals, Jour. Wash. Acad. Sci. 11, 1, 1921.

ART. XXXIII.-The Occurrence of Calcareous Sandstone in the Recent Delta of Fraser River, British Columbia, Canada; by W. A. JOHNSTON.

The occurrence of calcareous sandstone, which is apparently forming in the Recent delta of Fraser river, British Columbia, was brought to the attention of the Geological Survey, Canada, by samples sent in by Mr. W. P. Gross, Engineer of the Department of Public Works, in charge of dredging on Fraser river. The occurrence was examined during the course of an investigation, made during parts of 1919 and 1920, of the characteristics of Fraser river and its delta, and, because of its rarity and unusual character, is here described.

The Recent or modern delta of the Fraser river is building out into fairly deep water in the Strait of Georgia. The delta extends inland for 19 miles and across its seaward front is 14 miles wide. The surface of the delta is practically all below the level of high tide, and the delta land high enough to be reclaimed is diked. Sand banks, exposed in large part at low tide but completely submerged at high tide, form the seaward part of the delta and extend on an average 4 to 5 miles from the higher delta land. A number of distributaries flow through the delta, the main Fraser flowing the central part, the North Arm along the northern side of the delta, and in the southern part a number of smaller outlet channels occur.

The calcareous sandstone occurs in the sand banks in the seaward part of the delta. It was dredged by the Government dredge near the inner end of the entrance of the North Arm of the Fraser, where a bar was cut through and large quantities of the material thrown out. It was also dredged by the Government dredge and by the writer in the main channel of the river in its seaward part, and by the writer in the seaward part of the old channel of the river south of the present main channel. It is known to the fishermen, who refer to it as "clinkers" and state that it frequently fouls their nets in the channels on the sand banks both north and south of the main outlet channel of the river. It probably does not form in the river channels but in the sand banks, and occurs in loose masses in the channels because of erosion of the sand. Published by permission of the Director of the Geological Survey, Canada.