436 



NA TURE 



[March 8, 1894 



characters, without destroying them or forcing their 

 removal by the introduction of strange or exotic forms." 



The second volume of the Monographs (No. xviii.) de- 

 scribes the Gastropoda and Cephalopoda of the New Jer- 

 sey Marls and accompanying beds; the Lamellibranchiata 

 and Brachiopoda having been already the subject of a 

 memoir (No. ix.). These deposits are generally glauco- 

 nitic ; the fossils are casts, often ill-preserved, so that 

 the determination of them has been not seldom attended 

 by great difficulties ; they bear a superficial resemblance 

 to those from the Cambridge Greensand of England, and 

 the rock contains a certain proportion of phosphate of 

 lime, though these casts do not appear to be, strictly 

 speaking, phosphatised. The Marls, as is well known, 

 are mostly Cretaceous in age, no part representing the 

 Neocomian, but the uppermost beds are referred to the 

 Eocene Beneath the last are indications of a very 

 slight break : so that systems which in our own country 

 and the adjacent parts of Europe are separated by a wide 

 gap, in this region are practically continuous. The 

 beds— which may possibly be Neocomian — beneath the 

 Marls, called the Raritan clays, are brackish or even 

 fresh water in origin ; the Marls themselves are 

 marine, but shallow water deposits. The Cretaceous 

 members contain the usual cephalopods, which come 

 chiefly from the lower Marls, as indeed do most of the 

 other fossils. Among these are seven species of Am- 

 monites, four of Scaphites, and three of Baculites ; 

 Turrilites, Heteroceras, Ptychoceras, and Belemnitella 

 are each represented by one species. None, however, 

 appear to be individually common, and most are rare. 

 The Eocene contains one Nautilus and one Aturia. The 

 Gastropoda are fairly numerous, 136 in the Cretaceous 

 and 52 in the Eocene. As the former volume showed, 

 the Lamellibranchiata are more strongly represented in 

 the Cretaceous than in the Eocene, and in the former 

 deposit dominate over the Gastropoda ; the Brachiopoda 

 are in neither numerous. The illustrations in this volume 

 exceed fifty plates. 



The eleventh annual report is in two parts. Thefiro*:, after 

 the usual official matter, contains two lengthy memoiis ; 

 the first, almost a volume in itself, by Mr. W. J. McGecer - 

 titled the " Pleistocene History of North-Eastern Iowa,*' 

 the second, by Mr. A. J. Phinney, on the " Natural Gas 

 Field of Indiana," with an introduction by the former 

 author. In the "Pleistocene History" Mr. McGee 

 gives a very full and interesting account of the drifts of 

 a large area of Iowa, with maps illustrative of the con- 

 clusions which he considers them to justify. The region 

 appears to have been twice invaded by ice, the earlier 

 glaciation being " the longer and the more energetic." 

 Glacial strise, however, are very rarely found, in conse- 

 quence, probably, of the incoherence of the rock masses 

 to this region. As memorials of these invasions of the 

 ice-sheet, an upper and lower till can generally be dis- 

 tinguished ; and the latter sometimes shows crumplings, 

 interpreted as memorials of the pressure of the second 

 ice-sheet; between these tills a kind of " forest-bed " is 

 frequently to be found. By each advance of the ice- 

 sheet, rivers were dammed and great lakes formed on its 

 margin, in the waters of which materials were deposited 

 from the ice and from other sources, much of this being 

 a stiff clay, locally named "gumbo." During the first 

 invasion the land sank ; perhaps sufficiently to allow of 

 an invasion of the sea. A similar but less extensive sub- 

 sidence took place in consequence of the second invasion. 

 These depressions aided in the formation of the lakes. 

 A summary this, necessarily very imperfect, but it may 

 suffice to indicate the general conclusions at which the 

 author has arrived. 



The second memoir contains a vast amount of informa- 

 tion concerning the natural gas and oil wells of Indiana, 

 and is prefaced by a general sketch of the distribution of 

 bituminous deposits. The commercially valuable bitu- 



NO. I 27 I, VOL. 49] 



mens occur (not in America only) in the Lower Silurian 

 rocks, and continue to comparatively recent times, but 

 the most important are found in the Silurian and 

 Devonian systems, and in the Tertiary series. In the 

 first the products are chiefly gas ; in the second both are 

 found, petroleum probably predominating ; while in the 

 third nearly all the known forms occur. 



The second part of the report deals exclusively with 

 irrigation. Maps and details of the arid region of the 

 United States are given, from which it appears that 

 this extends from their northern frontier to the 32nd 

 parallel of latitude, and from the eastern slopes of the 

 Sierra Nevada approximately to the looth parallel of 

 longitude, thus including the great Inland Basin and the 

 Rocky Mountains. On the ranges, however, there is a 

 considerable amount of precipitation. As stated by 

 Major Powell, in evidence before a Committee of Con- 

 gress, the rainfall on the mountains may vary from 25 to 

 60 inches per annum, while in the valleys below it is 

 generally less than 15, and sometimes even as small as 

 3 inches. 



These publications, as this imperfect sketch may indi- 

 cate, are full of varied and valuable information, and are 

 richly illustrated with maps, plates, and woodcuts. If we 

 might venture on a general criticism, it would be that the 

 authors not seldom exhibit a tendency to " spread them- 

 selves " too much, to be over-diffuse in style, and to enter 

 upon general disquisitions, which, however interesting, 

 are a little out of place in official publications. Space 

 also seems occasionally to be wasted in giving informa- 

 tion which would be more appropriate in a text-book of 

 geology. As the volumes are primarily designed for the 

 people of the United States, the authors may be pre- 

 sumed to know best the desires of their own public, but 

 this redundancy is sometimes a little wearisome to out- 

 siders. Possibly the recent reduction of the vote for the 

 support of the Survey, which we trust will not be per- 

 manent, may be intended as an expression of this 

 fueling. Very probably some economies might be 

 effected, but it will be an ill day for this branch of 

 science if the work of the Geological Survey of the 

 United ;£tates is seriously cramped. 



T. G. BONNEY. 



MEASUREMENTS OF LOW VAPOUR 

 PRESSURES. 



THE two well-known methods of measuring vapour 

 pressures are the statical and the dynamical. In 

 the former the pressure exerted by a vapour is measured 

 when the substance is kept at a given temperature, while 

 in the latter the temperature is ascertained at which the 

 liquid boils when under a given pressure. The present 

 volume is mainly concerned with the description of, and 

 the results obtained by, a dynamical method of estimating 

 very low pressures for mixed as well as for pure sub- 

 stances ; the pressure range extending, in general, from 

 about zero to a maximum which is below 70 mm. 



Before proceeding to the description of this method, 

 the author seeks to clear away certain discrepancies 

 which have been recorded regarding the results of vapour 

 pressure observations as given by the statical and dyna- 

 mical methods. Dynamical observations on the fatty 

 acids, published by himself in 1885, differed consider- 

 ably at low pressures from those obtained by Landolt 

 in 1868 from statical measurements. From the fact 

 that the differences varied regularly with the chemical 

 nature of the acids, it appeared possible that at very 

 low pressures the two methods led to different re- 

 sults. A historical summary of work on this subject is 



1 " Studien fiber Dampfspanukraftsmessungen." In Gemelnschaft mit 

 Paul Schroeter und andern Mitarbeitern von Georg W. A. Kahlbauin. 

 asel : Benno Schwabe, 1893.) 



