658 



SCIENCE.. 



|Vou 11., No. 41. 



chauge in the relation of land and water 

 during fifty- four j-ears, and the mean level 

 of the Baltic results with a probable error of 

 ±6.1 mm. The levellings to Constance and 

 to Amsterdam are published, and the mean 

 level of the North Sea is found 9.3cm. above 

 that of the Baltic. Computation of polar co- 

 ordinates between geodetic and astronomical 

 points. Determination of latitudes and azi- 

 muths. Maximum local deflection of the 

 vertical reaches 6".l in the meridian, and 

 12". 7 in azimuth. 



Roumania. — Astronomical determinations of 

 positions. 



Russia. — Connection of the triangulation of 

 Bulgaria with that of Russia ; astronomical 

 detei-mination of diiferences of longitude, 

 connecting Bulgaria with Pnlkowa, and Tiflis 

 with the triangulation of the Caucasus ; pen- 

 dulum observations continued in th(5 Cauca- 

 sus ; extension of the levels of precision 

 (double measures) up to date, 4,123 km., 

 and of single lines 618 km. 



Saxonj', Germanj'. — Publication of part i. of 

 the third section of the astronomical and 

 geodetic observations, comprising ten sta- 

 tions ; recomputation of the base at Gross- 

 enhain. 



Switzerland. — Additions to the triangulations 

 to connect astronomicallj^ determined posi- 

 tions, and two new base-lines at Weinfelden 

 (length 2. .5 km.) and at Bellinzona (length 

 3.2 km.), both measured with the Spanish 

 apparatus of Ibanez ; mean error of measure, 

 ■ 6ooi„„o for the Aarberg base of 1880, 

 wirJwo and ^nnrk-oo ^or the other two bases 

 respectively. The coefficient of expansion of 

 the iron bar of this apparatus had increased 

 during twenty years ^ part. After sixteen 

 years of labor, the operations of levels of 

 precision have been brought to a close. 



Spain. — Determination of the length of the tri- 

 angle side, Mulhacen-Tetica (82827.546 m. 

 ± 0.115m.), of the great quadrilateral con- 

 necting Spain with Algeria ; adjustment of 

 the triangulation connected with the base 

 of Olite ; junction of the Balearic Islands 

 with the mainland, and observation of one 

 side, of 240 km. in length (Desierto to Tor- 

 rellas) , during the night, by means of electric 

 light ; tidal and levelling operations ; deter- 

 mination of the longitude between Madrid 

 and Badajos ; gravity measures at Madrid. 



"VVurtemberg, Germany. — Connection of lines 

 of spirit-levellings with levels of the Black 

 Forest. 



Belgium. — Comparison of results of the ad- 

 justed triangulation. 



Norwaj-. — Results of the difference of longi- 

 tude of Christiania and Bergen, and of two 

 base-lines with probable errors of i.-.^ooot) 

 and T75U JuTTo of their length ; adjustment of 

 a base-connection with a primary line involv- 

 ing flftj'-three conditional equations. 

 In conclusion, Yvon Villarceau presents a 

 paper on observations made at Paris with ai» 

 isochronic regulator in connection with his new 

 method for relative measui'cs of gravit}' ; the 

 apparatus, however, had not j'et been brought 

 to the desired perfection. C. A. S. 



TRYON'S CONCHOLOGY. 



Structural and systematic conchology (eic.^. By 

 George W. Tryon, Jun. Vol. ii. Philadel- 

 phia, the autlior, 1883. 430 p., 69 pi. 8°. 

 The second volume of Mr. Tr^'on's work 

 has appeared with commendable promptness. 

 It contains a discussion of the Cephalopoda, 

 Pteropoda, and the Gastropoda, beginning with * 

 the pectinibranchs, as far as and including the 

 nudibranchs. The classification is, of course, 

 the same as that criticised by us in the first 

 volume, and cannot be said to improve on 

 closer acquaintance. Some of the allocations 

 seem particularlj' inadvisable. For instance r 

 Scissurella, usuallj' regarded as of familj- rank, 

 is combined without reserve with Pleurotoma- 

 ria in one familj-. The Bellerophontidae are 

 retained in full familj- rank ; and yet they are- 

 with great probability, as suggested by Meek, 

 onl}^ large, sj'mmetrically rolled Emarginulas, 

 which latter are put in a different suborder, 

 with the true Limpets, to which thej- have no 

 close relation , and divorced from the Ilalioti- 

 dae, which the}- more nearly resemble. 



The order Pol3-placophora is defined (p. 

 103) as having the " shell multivalve, consist- 

 ing of eight pieces inserted upon the baciv of 

 the animal, and surrounded by a mantle bor- 

 der ; " yet with the Chitonidae are placed, to 

 form this order, a family Neomeniidae, which, 

 to say nothing of other differences, have no- 

 shell at all. 



The order Pectinibranchiata is defined as 

 having pectiniform branchiae in a «avity above 

 the neck, ' having an external opening upon the 

 side of the neck,' dioecious, and with spiral 

 shells. 



The order Scutibranchiata is described as 

 having pectiniform branchiae in a cavit}- above 

 the neck, or at the lower edge of the mantle 

 around the foot, dioecious ; shell spiral or con- 

 ical, holostomate. 



The portions in italics are intended to cover 

 the Docoglossa, which do not belong with the 



