November 9, 1S93] 



A' A rURE 



pp. 91-121). Prof. Sollas discusses the origin of the ancient 

 quartzites, grauwackes, and slates in that district, and gives 

 drawings from microscopic sections to ilkistrate the evidence in 

 favour of their originally sedimentary nature. Paireontological 

 evidence is present in the form of numerous worm-tubes and the 

 doubtful organic remains known as Oldhamia radiata and 

 antiqua. The whole group is regarded as a deposit in the 

 tranquil sea of a period, probably Cambrian or pre-Cam- 

 brian, which he rather happily characterises as the " Age of 

 Worms." Just as in the Highlands of Scotland, this Irish area 

 has been subjected to great earth-movements, not only once, but 

 several times. First, in later Cambrian age, the sedimen- 

 tary rocks were rolled up into a series of anticlinal and 

 synclinal folds. Ordovician time saw the rocks once more lielow 

 sea level, and a second elevatory movement set in with extreme 

 slowness in Upper Ordovician time. The third period of move- 

 ment is of post-Carboniferous date, and of simpler character 

 than the two preceding, the flexures having in the main followed 

 those of the Ordovician movements. In his concluding pages 

 Prof. Sollas briefly refers to the absence of mesozoic and 

 tertiary deposits, the general characters of the glacial period, 

 and the distribution of the boulder-clay over the Dublin area. 

 Sketch maps and diagrams illustrate the paper. 



The effect upon the optical properties of a plate of quartz of 

 compressing it in a direction perpendicular to its axis has been 

 investigated by M. F. Beaulard, who publishes his results in 

 I he Joicr7ial dc Physique. A quartz plate was cut normally to 

 the axis and compressed laterally, thus superimposing a double 

 refraction, varying with the pressure, upon the rotatory power. 

 Allowing a beam of plane-polarised light to fall normally on to 

 the plate, he obtained inside the crystal two elliptic vibrations 

 propagated with different velociti'es and exhibiting after emer- 

 gence a certain difference of phase. These two vibrations in- 

 terfered and gave an ellipse whose elements could be experi- 

 mentally determined. The pressures were obtained by means 

 of a Perreaux dynamometer, varying from o to 530 kgr. per 

 square cm. The quartz was placed between two jaws which 

 could be made to approach each other by turning a screw. One 

 of the jaws was fixed firmly in a frame, the other moved on 

 guides which communicated the pressure to an elliptical pair of 

 springs, the amount being indicated on a dial through a rack 

 and pinion arrangement. The dynamometer was mounted on 

 two wooden platforms allowing of the orientation of the quartz 

 plate normally to the incident ray. The rest of the apparatus 

 consisted of a polariser, a quarter-wave mica plate, a pair of 

 quartzes with two different rotations, an analyser, and a spec- 

 troscope with eye-piece slit. It was found that the rotatory 

 power remains constant ; that the difference of phase due to 

 double refraction alone is proportional to the pressure, and that 

 the.angle between the major axis of the emergent ellipse and 

 the original incident vibration increases at first with the pres- 

 sure (for plates of given thickness), then oscillates, and at par- 

 ticular pressures the two directions are the same, so that at 

 some points the major axis turns in a direction contrary to the 

 natural rotation of the quartz plate. 



At a recent meeting of the Academie des Sciences (Paris), 

 M. Poincarc communicated an account of the experiments on 

 the velocity of propagation of an electric disturbance along a 

 wire, which have been carried on by M. Blondlot at Nancy. 

 The wires used were of "high conductivity " copper, 3 mm. in 

 diameter, and were fixed to the telegraph posts between the 

 Prefecture and the Maxeville Asylum, a distance of aboat one 

 kilometre. The method employed was very like that used by 

 Wheatstone in his attempt to measure the velocity of the pas- 

 sage of an electric discharge, only instead of a rotating 

 mirror M. Blondlot uses a rotating photographic plate. Matters 

 NO. 1254. VOL. 49] 



are so arranged that twosparks pass between two knobs, one 

 direct and the other after travellin:; round the 2 kilometre 

 circuit. The mean of five experiments gives a velocity of 296 

 kilometres per second, the retardation being ^\^, of a second. 

 On a line 2 kilometres long, that is, one where the electricity 

 has to travel over 4 kilometres, the velocity obtained was 

 slightly greater, namely 29S kilometres per second. 



In a paper read before the American Institute of Electrical 

 Engineers, Messrs. Bedell, Miller, and Wagner give an account 

 of a new form of contact-maker which they have employed in 

 their experiments on transformers. The contact-maker was 

 required to connect for an instant a voltameter with the circuit 

 of the transformer at any required part of the cycle. The in- 

 strument consists of discs carried by a spindle which was con- 

 nected to the shaft of the dynamo. A needle projects from the 

 face of this disc and forms one of the electrodes for making 

 contact, the other being formed by a fine water-jet issuing from 

 a nozzle which is insulated from the rest of the instrument. The 

 water-jet is supplied by a jar of water, several feet above, the 

 connection being through a rubber tube. The nozzle of the 

 water-jet is carried by a disc which is capable of being rotated, 

 and has its edge graduated in degrees. The needle cuts the 

 water-jet near the nozzle before ihs continuous column has had 

 time to break up into drops. It was found necessary to put a 

 little salt in the water, as pure water does not work, while 

 acidulated water corroded the nozzle. This form of contact- 

 maker the authors find far superior to any of the usual mechani- 

 cal devices, the contact being perfectly constant and reliable. 



In the Zeitschrift fiir physikalische Chemie, vol. xii. No. 4, 

 Ilerr Humburg gives an account of a significant piece of work 

 which was undertaken for the purpose of obtaining additional 

 evidence as to whether the magnetic rotatory polarisation of 

 solutions gave any support to the hypothesis of electrolytic 

 dissociation. Measurements were made on solutions of the 

 lower fatty acids in water, benzene, and toluene. The mole- 

 cular rotation of the dissolved substance was calculated on the 

 supposition that the value found for the solution was the sum of 

 those given by the amounts of solvent and dissolved substance 

 which it contained. The numbers thus obtained were found to be 

 practically independent of the concentration and of the chemical 

 nature of the solvent, and were identical with the values given 

 by the free acids. Not only was this the case with acids such as 

 acetic, proponic, and butyric, which are held to be but feebly 

 dissociated in aqueous solution, but also of the chlor-acetic 

 acids, which are supposed to be much more strongly dissociated. 

 Similar results were -obtained from observations on solutions of 

 various inorganic; salts, such a^ potassium iodide, sodium 

 bromide, ammonium nitrate, and barium bromide in water, and 

 in methyl alcohol. Although the molecular conductivity of the 

 aqueous solution of any of the salts was invariably much greater 

 than that of the alcoholic solution, nevertheless the molecular 

 rotation of the salt was the same in both cases. In con- 

 junction with the work of Schonrock on this subject (see 

 Notes, vol. xlviii. p. 230), the above results indicate that the 

 effect of electrolytic dissociation on the magnetic rotatory 

 polarisation of solutions (if such an effect really exists) is too 

 small to be detected by ordinary methods of measurement. 



Although such a large number of investigations have been 

 made on the bacterial contents of waters derived from such 

 different sources as lakes, rivers, springs, and wells, only a few 

 observations have been made on the microbial C(ondition of sea- 

 water. Giaxa's are the earliest recorded examinations, and 

 exhibit the poverty in this respect of sea-water. Thus, in the 

 Bay of Naples, at about a mile and a half from the shore, only 

 ten organisms were found in I c.c. Russell, also working in 

 this bay at distances of 2\ to 9 miles from the coast, obtained 



