concretionary limestones were originally dolomitic limestones, and there can be little doubt that these rocks were impregnated with sulphates and that the solution of these brought the bed into a condition which gave the concretionary forces full play; and further it would seem highly probable that the complicated structures occurring in these rocks were mainly produced when the beds were saturated in solutions of calcium sulphate containing colloidal organic matter. It is the presence of this latter matter that causes the spheroidal condition."10 From a study of the few specimens at hand, the inorganic and secondary character of the structures seems also to be evident. What is observed at once, both in the field and in the literature, is that there generally is in these structures every transition between the various types, and that hence they can not well have the value of "genera" and "species." Abbott, who speaks of the "hundred or more patterns met with," like Woolacott, distinguishes several main types (Abbott's honeycomb and coralloid; Woolacott's spherical and cellular), and these again each divide into minor varieties, but that is all that can be done with them. We may find any sort of variation and transition. As Sedgwick says, there is no end to the modifications. The thickness of the laminæ varies, and the distinctness of the radiating structure as well. In figure 6 very different characters can be seen in this one specimen. In the lower part, only the concentric lamina are seen, while in the upper left-hand part, radially arranged tubes are very distinct. These tubes or rods come into existence by more or less conspicuous thickening of the concentric lamina at regular intervals. The tubes can also be very slender, and the concentric lamina only slightly indicated, as in figures 7 and 8 (top). One feature that does not vary, however, is the arrangement of these radiating rods or indications of rods vertical to the concentric lamina. Where the lamination curves, the directions of rods change correspondingly. In the upper part of the specimen illustrated in figures 4 and 5, the tubes are straight and parallel, and here we find a totally regular lamination, with the laminæ in a "The possibility of a primary deposition has, however, been mentioned by Jukes-Browne (Geol. Mag., 1891, p. 528), and B. A. Green has suggested (see Woolacott 1912, p. 270) that the rock was originally a tufaceous deposit, the concretions being in part due to irregular precipitation, and in part to later rearrangement. plane and quite parallel. This lamination is, however, of another type than the more coarse irregular one which is seen in the lower part of the same specimen. This exceedingly fine lamination seems, to judge from the pieces at hand, to be secondary in relation to the coarser one. A similar lamination can also be observed in figure 6, cutting through the coarser structure. A fine lamination that might correspond to the one seen in my figure 6 seems also to cross the coarser structure of the Newlandia frondosa in the specimen depicted in Walcott's plate 6, figure 3. This lamination probably corresponds to the "bands" of Abbott (1900), which, as he says, "run across the beds at various angles." He states further that "the rods invariably start from the last-mentioned bands, and may be seen at every angle." The regular, "basaltic" tubes, the Greysonia structure, thus are connected with one type of lamination, the more irregular radiating rods or indications of rods of the Newlandia structure with another, and as both types of laminæ are seen crossing each other, they can not well both represent a primary structure, coming into existence at the time of deposition. Even without this crossing, one would judge that a structure like that shown in figure 4 is too geometrically regular to have anything to do with organic deposition. Walcott also remarks (p. 109) concerning the Greysonia that "it is difficult to conceive of the tubular structure of Greysonia as a deposit made by algæ, but with the example of the varied forms of recent deposits made by the blue-green alga (Cyanophyceae) and the other fossil forms described in this paper we are prepared to consider Greysonia as of algal origin." As far as can be judged from my specimens, the coarser Newlandia structure cannot be of organic origin. An individual like the one in figure 3 shows so great a regularity that only one of two conclusions can be drawn: either it represents a true organic skeleton, like that of a huge Nummulites or Receptaculites, or it must be wholly of inorganic origin. The recent "lake balls" that Walcott figures have no regular radiating structure at all, nor should such a structure be expected in a deposit of that character. That we have a true skeleton no one assumes; on the other hand, the regular spherical laminæ of figure 3 may in other specimens be quite irregularly undulating, as in figure 6, or practically straight, as in figure 5, lower part. To judge from the specimens figured, without taking into account the general view of the structures in the rock, the only possible explanation other than that the structures are due to secondary "concretionary" changes in the sedimentary mass, is that we have here structures that might be compared to stromatolites and oolites primary deposits, yet not of a character that would justify the introducing of generic and specific names. Yet there are fundamental differences between oolites and the specimens shown in figures 1 and 3, and between stromatolites and specimens like those in figures 2, 5, and 6. First among these differences is the great thickness of the lamina when compared to the delicate laminations of oolites and stromatolites (the corresponding hot-spring and "sinter" calcareous deposits included); another is the very considerable dimensions of the spherical bodies here shown, a parallel to which is not known from recent deposits. In addition, we see that the spherical bodies often pass with their lamination into each other, as may very distinctly be seen in parts of the specimen depicted in figure 3, and even more so on the other side of the specimen. The spheres are parts of a large coherent mass. This feature contrasts decidedly with the ordinary oolitic structure, but is not infrequently seen in typical concretions, e. g., in chert nodules where the lamina may be arranged around different centers, yet the outer laminæ of one sphere pass into the corresponding ones of the neighboring spheres. In the botryoidal concretions so common in the Fulwell quarries, we have great clusters of coherent spheres that suggest a somewhat similar mode of formation. A most important feature of difference is the existence of a sometimes extremely strongly marked radiating element in the Permian structures; a similar type of radiating rods is not known in stromatolites and oolites. When there is a radiating structure in oolites, it is due to crystal fibres, while the rods of the structures here figured are made up of fine-grained-sometimes extremely fine-grained-limestone. We may have tube-like structures in the stromatolites, indeed these are very typical, but these tubes are, when the rock is in an unchanged condition, not at all of a similar regular type."1 Thus, judging from the general characters of the speci"How a secondary chemical change of the rocks tends toward giving a more regular, geometrically arranged pattern is illustrated in the regularity of the silicified tubes in the stromatolite layer from the Alten district figured in my article on Finmarken of 1919 (p. 93), when compared with the figure on page 91 of the same paper whch shows the typical irregularly tubular stromatolite structure of an unaltered dolomite. mens illustrated in this paper, we are brought to think of all these structures, as do the English geologists, as being formed secondarily by very important radical internal changes in the rocks. It has also been pointed out by several of these investigators-and I wish to emphasize this fact-that some of the characters of these structures suggest those developed by crystallization processes. Abbott (1900) points out the likeness of the "lines" and "planes" in the concretionary beds to the "lines which shoot across congealing water." I might mention especially that the regular right-angle relation between the direction of the concentric and vertical element of the structures seems to be of a similar character to the right-angle relation so commonly seen between the direction of the crystal fibres and the concentric laminæ in a laminated crystalline rock, taking as an example a piece of laminated, fibrous, crystalline aragonite like the one the structure of which is indicated in the lower drawing of figure 8, or the well known radiating fibres of calcite (or pyrite which by metasomatic change has taken the place of calcite) in an ordinary lime concretion. That the changes in these rocks in general have been great can not well be doubted, and this fact is certainly proved by the English investigators. Yet it is in the residual material of a rock with a cellular structure similar to that which is so common in the Durham limestone that the extremely delicate chains of cells representing parts of blue-green alga were observed. In sections of specimens of Gallatinia pertexta, a "species" which, as emphasized also by Walcott, is certainly very septaria-like, are reported minute remains of bacteria. This fact may not seem to harmonize very well with the idea of great internal changes in the rock, but we have only to consider how very delicate structures are often preserved in concretions of lime or of silica, where a transportation of mineral matter has also taken place, to realize that the secondary character of the rock and the occurrence of minute cells of plants are not mutually exclusive phenomena. The discovery of algae and bacteria in pre-Cambrian strata, reported by Walcott, has therefore lost none of its importance, even if it should be found that these organisms are not responsible for the many curious structures found in the Algonkian Newland limestone. University, Kristiania, October, 1920. SCIENTIFIC INTELLIGENCE. I. CHEMISTRY AND PHYSICS. 1. Perchloric Acid as a Dehydrating Agent in the Determination of Silica.-H. H. WILLARD and W. E. COKE, of the University of Michigan, have found that the use of perchloric acid gives marked advantages over the usual methods for this very frequently required analytical determination. The dihydrate of perchloric acid, HCIO,.2H,O, boils at 203°C, and at this temperature is a powerful dehydrating agent. Nearly all its salts are soluble in the strong acid and in water, presenting in this respect a great advantage over sulphuric acid for this purpose. The pure acid has been on the market for some time, and although still rather expensive it could be made more cheaply if there were sufficient demand for it. The method as applied consists in dissolving the metal or silicate in hydrochloric or nitric acid, adding perchloric acid, or dissolving directly in perchloric acid, evaporating to dense fumes of the latter, boiling gently, in a covered beaker to avoid undue waste of the acid, for 15 or 20 minutes to dehydrate the silica, cooling and diluting with water. All salts are instantly soluble and the silica is filtered off and determined as usual. It contains less impurity than when separated by the usual methods. Moreover the silica remaining in solution is much less than in the usual method of evaporation to dryness and treatment with hydrochloric acid, so that except for the most accurate work it can be neglected. The operation is simple and rapid. Test analyses made by the authors upon very pure quartz sand (after fusion with sodium carbonate), upon cements, limestones, samples of willemite, irons, steels, aluminium and nickel gave very good results. It seems probable that this new method will find extensive application, both in scientific and technical analysis. Jour. Amer. Chem. Soc., 42, 2208. H. L. W. 2. The Chemistry and Crystallography of Some Fluorides of Cobalt, Nickel, Manganese and Copper.-It is sometimes desirable, perhaps, to call attention to a chemical article for the purpose of showing that it is unsatisfactorily presented. Such appears to be the case in this article by FLOYD H. EDMISTER and HERMON C. COOPER, which takes up about 15 pages of an important chemical journal. They have described the acid fluorides CoF2.5HF.6H2O, and CuF..5HF.6H,0. |