represent the relation here involved. The constants of the lines drawn through the points are given at the end of the tables in §§ 3, 4 and 7. In the cases of silver, of gold, of platinum and of steel, the distribution of the points with reference to these lines is satisfactory, when the errors introduced by the mechanical treatment, by variations of hardness, and particularly by imperfect homogeneity are justly taken into account. In many cases, moreover, the percentage presence of foreign ingredient is greater than that specified in § 1. As all this is even more frequently the case with alloys of the oxydizable metal copper, the line computed by the method of least squares does not fairly represent these observations. The exceptional points here are the alloy of Cu with 22.4 per cent Ag, and the brasses with 23.6 per cent, 29.4 per cent and 42·1 per cent Zn. If these high per cents are rejected, the line for copper* will agree more nearly in character with the lines for gold and for silver, as it will tend more nearly to intersect the origin of coördinates (smaller numeric m). Applying the method of least squares for the case in which the inadmissible copper alloys are withdrawn, I find m=-0.278 and n=+0·005655, and of course a better agreement between observed and calculated a throughout. In figure 2, however, I have nevertheless inserted the line calculated for all the copper alloys in hand.

An interesting peculiarity of the steel line is that it leads to a larger value for the temperature-coefficient of iront than that hitherto accepted. Comparisons of absolute values must however be made with caution, because of the great variety of electrical standards used by different observers. The high temperature-coefficient of iron is in conformity with relatively high values usually shown by alloys containing iron (cf. fig. 1.)

I desire finally to advert to the occurrence of the relatively small values of the constant, m, as computed for each of the series of silver, copper, gold, platinum and steel alloys. There is a marked tendency in all the cases stated to intersect the coördinate axes very near the origin. Inasmuch therefore as (§ 1) a =ƒ'(x,0)/ƒ(x,0) and λ=1/ƒ(x,0), the slopes of these lines are very nearly equal to f'(x0); or more rigorously to f'(0,0), since their true nature is that of an initial tangent (cf. §3.) In 811 it appears that I am not asserting, however, that these lines do pass through the origin.

* Those who have worked with copper alloys, will know the extreme difficulty encountered in making the individual points conform to any uniform curve. The data usually make up a diagram of very broken lines, as in the above work of Matthiessen, and in results of Dr. Strouhal and myself. Further comment is made in the Bulletin.

In his research on the conductivity of iron, Auerbach (Wied. Ann., viii, p. 479, 1879), discusses reasons for the exceptionally high value of the temperaturecoefficient of iron.

11. Taking the results collectively, they point to a limit below which in the case of solid metals and at ordinary temperatures, neither electrical conductivity nor temperature-coefficient can be reduced; whence it appears that a lower limit of both conductivity and temperature-coefficient is among the conditions of metallic conduction, not to say of metallic state.* These considerations are suggestive and I shall therefore endeavor to make what I have in mind clearer. In the case of conduction in metals (solid or liquid) the effect of temperature is a decided decrease of conductivity, continuing apparently, as temperature increases, indefinitely. In the case of conduction in non-metallic elements or in electrolytes (solid or liquid) on the other hand, the effect of temperature is a decided increase of conductivity, which supposing the liquid state to be retained, continues as temperature increases. Hence conduction in metals is distinguished from conduction in electrolytes in this respect, that if the temperature coefficient in the one case (electrolytes) be regarded positive, its value in the other case (metals) must be negative. This leads me to inquire into the possible occurrence or the nature of a class of substances whose temperature-coefficient is zero; a class of substances in other words in which the metallic and the electrolytic modes of electric conduction may be supposed to converge.§

The point which I have in view, viz: the possibility of a continuous transition from metallic to electrolytic conductivity gains much in reasonableness by associating with good metallic conductivity the correlative property of optic opacity. Relations between electricity and light have been investigated and many experimental facts are known. Maxwell's electro-mag

* Recent researches of v. Ettingshausen and Nernst and of C. L. Weber (Wied. Ann., xxxiv, p. 582, 1888), show that the resistance-temperature coefficient of bismuth is often negative between 0° and 100°. Edward Weston has made alloys of copper, ferro-manganese and nickel of which this temperature-coefficient is nearly zero or even negative (Science, xii, p. 56, 1888). These exceptions, the underlying cause of which is probably secondary and to be referred to structural or crystalline modification, emphasize the vast amount of evidence in favor of the normal behavior given in the text. I may add, for instance, that the temperaturecoefficient of glasshard steel between 0° and 100°, would be nearly zero because of annealing.

Following Benoit (C. R., lxxvi: p. 342, 1873) the electrical resistance of all metals increases with temperature at an accelerated rate, except in the case of platinum and palladium, where the rate of increase is retarded. Benoit observes at temperatures limited by the boiling point of zinc.

Matthiessen (Pogg. Ann., ciii, p. 428, 1858), W. Siemens (Wied. Ann., x, p. 560, 1880) and others (Bergmann, Kemlein, Muraoka) find this to hold for modifications of carbon. Similar increases of conductivity are usually observed in the case of selenium and tellurium (Hittorf, W. Siemens, Mattheissen, and many others); but the relations here are complicated. Quite recently Duter (C. R., March 19th, 1888) has shown that sulphur conducts at its boiling point. It is this investigation which I have specially in mind in the text.

§ Something of the kind may perhaps occur in the case of some natural sulphides, but it is not open for systematic study and its nature is obscure.

netic theory of light furnishes a theoretical basis for the fact that true conductors are exceedingly opaque. The resistance of solid metals, however intensely they may be heated, is found to increase so long as temperature increases. Nevertheless the careful experiments which Govi* made to interpret an erroneous result of Secchi,† prove that solid metals even in extreme states of white heat remain opaque. In the case of liquid metals at extreme white heat the case is not so definitely established; and the question relative to the ultimate transparency of liquid metals at very high temperatures is an open one.‡ It is in the direction of ultimate transparency that the observed continuous increase of resistance with temperature seems definitely to point.

It is reasonable to infer that the transition from opaque to transparents will take place in the region of the critical temperature. At least such transition must ultimately occur; and I am led to conjecture that the said transition from opaque to transparent will be accompanied by a change of the values of the electrical temperature coefficient, passing from the negative value which holds for the liquid metal, to the positive value which will probably hold for the gaseous metal, continuously through zero. The fact that conduction in gases is of an electrolytic nature was proved by Varley, who showed that after the polarization of the electrodes is overcome, gases obey Ohm's law. The electric strength of air is known to diminish rapidly as temperature is increased. Working with hot gases carefully insulated and protected from flames, Maxwell was unable to obtain conduction either in hot gases like air or in hot metallic vapor like Hg or Na. At higher temperatures (red heat) the researches of Blondlot,** confirming the observations of E. Becquerel,tt prove that hot gases are conductors, and that at temperatures sufficiently high volt is enough to set up a current. Hence in their thermal relations also, gases ultimately partake of the nature of an electrolyte, and the occurrence zero value of the temperature coefficient may be reasonably associated with the critical temperature of the metallic liquid, passing continuously from the liquid into the gaseous state.

* Govi, Comptes Rendus, lxxxv, p. 699, 1877. + Secchi, Comptes Rendus, lxiv, p. 778, 1867.

W. Ramsay, Chem. News, lv, pp. 104 and 175, 1887; Turner, ibid., p. 163, 1887; Professor T. Sterry Hunt has given the question some attention. Kundt's recent experiments (Wied. Ann., xxxiv, p. 469, 1888), on the refractive index of metals will doubtless lead to more definite results than the data now in hand. § The jet of liquid hydrogen escaping from Pictet's apparatus appeared steelblue, and was opaque for a distance of about 12cm.

Varley, Proc. Roy. Soc., xix, p. 236, 1871.

Maxwell, Elementary Treatise on Electricity, ed. by Garnett, 1881, §§138, 139. **Blondlot, Comptes Rendus, xcii, p. 870, 1881; ibid., civ, p. 283, 1887. ++ E. Becquerel, Comptes Rendus, lv, p. 1097, 1867.

ART. XLIV.—On the Puget Group of Washington Territory; by CHARLES A. WHITE.

[Published by permission of the Director of the U. S. Geological Survey.]

ABOUT two years ago, Prof. J. S. Newberry placed in my hands for study a small collection of fossil mollusca which he had obtained from the coal-bearing formation in Puget Sound basin in Washington Territory. This collection represents a hitherto unpublished brackish-water fauna, which characterizes a formation that possesses unusual interest. All the discovered species of this fauna will be described and illustrated in Bulletin 50 of the U. S. Geological Survey, where also the formation will be discussed. Twelve species have been recognized, of which the following is a list: Cardium (Adacna ?) ?, Cyrena brevidens, n. s., Corbicula Willisi, n. s., C. Pugetensis, n. s., Batissa Newberryi, n. s., B. dubia, n. s., Psammobia obscura, n. s, Sanguinolaria? caudata, n. s., Teredo Pugetensis, n. s., Neritina ?, Cerithium- ? and an undetermined gasteropod.

The formation from which these fossils were obtained is known to occupy a large part of Puget Sound basin, and to extend upon the western flank of the Cascade range, which forms the eastern side of the basin; but all the boundaries of the area which it occupies are not at present known. Besides. these strata which lie to the west of the Cascade range, other similar deposits are found upon its eastern flank, as well as at certain localities among its higher mountains. All these deposits are believed to belong to one and the same formation, although those within, and east of, the Cascade range have not yet furnished any molluscan fossils similar to those found upon the western side of the range. Certain unique features of the fauna referred to show that the strata in which the remains were found were deposited in a body of water which was quite separate from that in which was deposited any one of the coal-bearing formations in the Pacific Coast region or elsewhere. Its zoological character indicates that the body of water in question was an estuary; and the extent of the district within which the deposits have been found shows that that estuary was a very large one.

The most complete information that has yet been published concerning this formation appeared in volume xv of the reports of the Tenth U. S. Census, pp. 759-771, plates LXXXII-CII. That publication, which is entitled "A Report on the Coal Fields of Washington Territory," is by Mr. Bailey Willis, who accomplished the work upon which his report is based under

the auspices of the Northern Transcontinental Survey. The special object of his report having been the presentation of the coal resources of that region, the discussions are confined mainly to its coal-bearing formations; and the report therefore does not embrace a full account of the geology of the whole region. Still, Mr. Willis has given some comprehensive facts as well as many elaborate details concerning this formation in the report referred to; and as my own field labors upon the Pacific coast have not extended to the northward of the Columbia river, my knowledge of many of the facts which are stated in the following remarks has been derived from him, and from Professor Newberry.

The orogenic elevations of the Pacific Coast region extend in two lines which are approximately parallel with each other and with the coast. The eastern line consists of the Sierra Nevada in California and of the Cascade range in Oregon and Washington Territory. The western line, known as the Coast range in California, is more or less distinctly recognizable through western Oregon, and extends northward of the Columbia river into Washington Territory; but it there sinks to low hills before reaching the Olympic cluster of mountains, which forms the northern end of the line. This cluster is a prominent feature of that district, its higher peaks rising to more than 8000 feet above the sea level.

The relief of this great strong-featured Pacific Coast region is the product of several uplifts, differing in time, extent and locality, the whole history of which is not yet clearly understood but the facts of interest in this connection may be provisionally stated as follows. The Cascade range, which has been recognized as distinct in structure and origin from the Sierra Nevada range, although in a general line continuous with it, has been considered to be itself simple; but it is in reality quite complex. In Oregon it is composed of erupted material, often of great thickness, which has been observed to rest upon nearly horizontal sedimentary strata of Cretaceous age; and in southern Washington Territory it consists of enormous masses of erupted rocks overlying highly flexed sedimentary strata of late Mesozoic or early Tertiary age. In the northern half of the same Territory the range is made up entirely of granite, crystalline schists and volcanic rocks. As bearing upon the subject in hand, it may be stated here that the Tertiary rocks, which prevail in the Coast range generally seem to be wanting in the Olympics which, in this respect and in their composition, resemble the northern portion of the Cascade range.

Between the two long lines of orogenic elevation before referred to, lie the great valleys of the Sacramento and San Joa