February 8, 191 2] 



NATURE 



50: 



same progressive changes of morphological and physical 

 properties in the same direction as the rubidium and 

 caesium salts of all the other groups investigated, so that 

 if the potassium salt could be prepared the three salts 

 would undoubtedly form a eutropic group progressive in 

 properties in accordance with the atomic weights of the 

 three alkali metals, and it is even possible to predict the 

 properties of the missing potassium salt. As in all the 

 other cases, the ammonium salt is isomorphous, and not 

 eutropic. Moreover, the double chromates are isomorphous 

 and not eutropic with the eutropic sulphates and selenates. 

 — Prof. W. J. LeMris : A lead-grey sulpharsenite from 

 Binn, probably liveingite. The crystals have two 

 prominent zones mutually inclined at 90°, the one markedly 

 oblique and the other prismatic in symmetry. Assuming 

 oblique symmetry, the face-symbols are very high 

 numbers ; assuming anorthic symmetry, they are simple, 

 but the crystals possess several relations characteristic of 

 oblique symmetry, and twinning, though undoubtedly 

 occurring, is not a satisfactory explanation. — R. H. Solly 

 and Dr. G. F. H. Smith : A new anorthic mineral from 

 the Binnenthal. Since no further crystals have come to 

 light similar to the five minute ones found in 1902 by Mr. 

 Solly on a crystal of, probably, rathite, they have recently 

 been remeasured. They are lead-grey, and their streak is 

 chocolate in colour, and they are therefore probably a 

 sulpharsenite of lead. No axes or plane of symmetry were 

 observed, and the symmetry is therefore anorthic. The 

 fundamental constants are a:h : £ = 0-9787 : i : 1-1575 ! 

 a=ii6° 53I', 3 = 85° 12', 7=113° 44^'; 010:001=62° 41', 

 001 : 100 = 83° 4^', 100 : 010 = 65° 46'; and about twenty-one 

 forms were observed, of which the most prominent are 

 100, 010, 001, "iio, iTi, iiT. — Dr. A. Hutchinson : 

 Colemanite and neocolemanite. By a slight change in the 

 orientation adopted for the crystals of the latter mineral, 

 its crystallographic and optical properties can be brought 

 into harmony with those of the former. This can be 

 effected by a rotation of the crystal through 180° about 

 the normal to the face 001, 100 of neocolemanite then 

 coinciding with Toi of colemanite. — Dr. A. Hutchinson 

 and Dr. A. E. H. Tutton : Further observations on the 

 optical characters of gypsum. With the aid of new 

 apparatus, by which the section-plate of gypsum perpen- 

 dicular to the first median line can be surrounded during 

 observations of the interference-figure by flowing hot 

 water, of which the temperature is accurately recorded 

 both immediately before and after passing the crystal, the 

 authors have been able to prove definitely that the tempera- 

 ture at which gypsum becomes uniaxial is for sodium light 

 91°, for red C and greenish-blue F hydrogen light 89°, 

 and for the violet hydrogen line near G 87°. These 

 temperatures agree precisely with those observed for the 

 exact superposition of the pair of images of the spectro- 

 meter slide, afforded by a 60° prism cut to give the o and 

 /3 refractive indices. Owing to the large correction neces- 

 sary for conduction of the crystal holder, when the ordinary 

 Fuess air-bath heating apparatus was employed, and to the 

 difficulty in determining it, former determinations of the 

 temperature at which a section-plate of gypsum becomes 

 uniaxial were too high, and did not agree with the prism 

 observations. — Dr. G. F. H. Smith : Note on a large 

 crystal of anatase from the Binnenthal. The crystal 

 exhibits a combination of the forms a(ioo), t(3I3), and 

 2(113), 3"d the others not prominent, and it is remarkable 

 for the fact that the faces t have been entirely replaced 

 by numberless tiny crystals with the forms 2(113), fe(ii2), 

 ^(iii). and e(ioi), and the same orientation as the large 

 crystal. 



Geological Society, January 24.— Prof. VV. W. Watts, 

 F.R.S., president, in the chair.— Dr. C. A. Matiey : The 

 Upper Keuper (or Arden) Sandstone group and associated 

 rocks of Warwickshire. The stratigraphy of a sandstone 

 zone in the Keuper Marls of Warwickshire, well exposed 

 in the area formerly occupied by the Forest of Arden, is 

 ' described. This zone varies in lithological composition 

 and thickness. It is never wholly a sandstone, but always 

 contains beds of light grey and' pale green shale, marl, 

 and mudstone. The sandstone usually forms thin, flaggy, 

 white or light grey beds, and exhibits ripple-marks, 

 current-bedding, and surfaces with footprints and sun- 

 cracks. The zone contains Estheria minuta ; plants ; teeth, 



NO. 2206, VOL. 88] 



spines, and scales of fishes ; tracks and remains of laby- 

 rinthodonts and reptiles ; and occasional casts of moUuscan 

 shells. The zone was first described by Murchison and 

 Strickland in 1837, but has not hitherto been completely 

 mapped. The author traces it from the type-locality at 

 Shrewley over an area of 108 square miles, and finds that 

 it forms a continuous deposit at an horizon between 120 

 and 160 feet below the base of the Rhaetic. He accepts 

 the view of Murchison and Strickland, and he also corre- 

 lates with it the similar deposit at Leicester described by 

 Plant. The formation was probably formed, as an 

 episode in the history of the Keuper Marls, by an irrup- 

 tion of the sea into the Keuper Marl area. It represents 

 a phase corresponding to that of the Rhastic bone-bed and 

 the tea-green Marls, but of somewhat earlier date. The 

 author is inclined to the view of the older observers that 

 the Marls are aqueous deposits, though possibly contain- 

 ing much wind-borne material, deposited in a shallow lake 

 undergoing strong evaporation and subjected to occasional 

 irruptions of the sea. They represent the closing phase 

 of Triassic " continental " conditions in the English Mid- 

 lands, when the slow subsidence which was soon to bring 

 in marine Rhaetic and Liassic deposits was in progress, 

 and produced that overlapping of the Keuper rocks on to 

 the higher grounds of the Triassic land-surface which is 

 observable in the neighbouring districts of the Lickey 

 Hills, Nuneaton, and Charnwood Forest. The paper also 

 records three well-borings through the Marls into the 

 Lower Keuper Sandstone. 



Physical Society, January 26 —Prof. H. L. Calnelard, 

 F.R.S., president, in the chair. — R. Appleyard : A direct 

 reading instrument for submarine cable and other calcula- 

 tions. The logarithmic spiral has frequently been used 

 for determining by a graphic method the logarithm of the 

 ratio of two quantities. If an attempt is made to apply 

 the spiral to the solution of engineering problenis, such as 

 arise in the design of submarine cables, there is difficulty 

 in obtaining sufficient accuracy, especially for readings 

 near the pole of the spiral. This defect has been removed 

 by introducing a secondary spiral, similar in all respects 

 to the primary spiral, and having the same pole, but dis- 

 placed round the pole through a certain constant angle. 

 A pair of radial scales, each having its zero at the pole, 

 and each divided into the same number of equal divisions, 

 can be rotated about the pole. At all angular positions a 

 scale of this kind will be cut by the two spirals if they 

 are sufficiently extended. For all angular positions of 

 such a radial scale the distance between the pole and the 

 point where that radial scale is cut by the secondary spiral 

 is always the same multiple of the distance between the 

 pole and the point where the radial scale is cut by the 

 primary spiral. In effect, the secondary spiral magnifies 

 the radial scale readings of the primary spiral to any 

 desired extent, depending only upon the angle through 

 which the template of the primary spiral is rotated to form 

 the secondary spiral. The spirals are drawn in a manner 

 that avoids ambiguous readings, and give maximum 

 precision within the range of diameters of conductors and 

 dielectric coverings required for submarine cable work. 

 The instrument is provided with two similarly divided 

 radial scales, one corresponding to d, the diameter of the 

 conductor, and the other corresponding to D, the diameter 

 of the dielectric. The angle between the two scales, corre- 

 sponding to any pair of values of d and D, is then a 

 n'leasure of log'D/d. The scales can be marked to indi- 

 cate weights of conductor and dielectric, and the circle of 

 degrees to which the spiral is drawn can be marked to 

 indicate log D/d. capacity, dielectric resistance, and other 

 functions of D and d, if required, for any definite dielectric, 

 the specific constants of which are K"°^"- ^J"; jTf^* 

 - to the spiral may be wriftrn « = Alogd+B, 



; A 



por^'hrough anangie 0. This is equivalent to rotating 

 P°'V rJ .._j:„i o-oirc throiirth A. The intercepts are now 



• I the primary spiral is rotated backwards about its 

 „„.. through an angle 0. This is equiv.-i 

 bo h the radial scales through ^. The intercepts 

 d and D,-i.c. the radial scale readings are now greater 

 in the ratio n = j-f;.-S. Butt.rworth : The vibration 

 galvanometer and its .ipplirations to i"^"ctance bridges. 

 Vibration galvanometers are divided into two types, accord- 

 ing as their moving parts possess only one or an mfinite 



