Feb. 5, 1880] 



NATURE 



327 



bottom of the Polar Sea ; for example, at a depth of 

 between 20 and 100 fathoms in the middle of Hinloopen 

 Strait in Spitzbergen, on the east coast of NovayaZemlya, 

 in the sea east of Cape Chelyuskin, and south of 

 Behring's Straits. At these places the temperature of 

 the sea all the year round is between 0° and - 2° - 7 C. 

 A temperature at or under the freezing point appears 

 thus to be much more favourable for the development of 

 an abundant animal life at the sea-bottom than one of 

 15 to 25 C, a very remarkable circumstance, which, 

 as far as Nordenskjold knows, has not received the 

 attention which it deserves. It is to be remarked, how- 

 ever, that the invertebrate animals in the south are larger 

 and finer than in the north, and that the shore fauna, 

 which is entirely absent in the sea of the high north on 

 account of the destructive action of the drift-ice, is here 

 richly developed. 



Japan is so poor in land- and fresh-water Crustacea, 

 that one often searches for hours in the most favourably 

 situated places without finding a single specimen. Even 

 in the most northerly part of Scandinavia more land 

 Crustacea may in many places be collected in a few hours 

 than in Japan in as many days. Lieut. Nordquist, how- 

 ever, has made a fine collection, which is expected to 

 yield many interesting new contributions to the fauna of 

 Japan. 



In the numerous dredgings carried on during the 

 voyage from Japan to Ceylon at depths in which algae 

 are met with in abundance on the coasts of Scandinavia, 

 not a single alga was brought tip by the dredging appa- 

 ratus. Even in the shore belt marine plants are in many 

 places almost wholly wanting. Some places were found, 

 however, more fortunately situated. The observations 

 made here and the information obtained by an examina- 

 tion of the collections in the museums of Tokio have 

 enabled Dr. Kjellman to obtain a general view of the 

 occurrence of algae on the east coast of Japan of special 

 interest in many respects in connection with researches 

 carried on by him during the preceding part of the 

 voyage, for example, with respect to the boundaries of the 

 areas occupied by different algae, with respect to the 

 mutual relation between the abundance of individuals 

 and species at different places, and with respect to the 

 types which are to be considered distinctive of the dif- 

 ferent areas. 



The lichen flora of Japan was examined by Dr. Alm- 

 •quist. In the more elevated regions, as on the sides of 

 the mountain Fusijama, 13,000 feet high below the snow 

 limit, at a height of 6,000 to 8,000 feet above the sea, it 

 has a certain resemblance to that of Scandinavia, but in 

 the low country it is limited to a very few localities. In 

 the purely tropical countries, for instance at Labuan and 

 Singapore, the lichens appear to be confined almost ex- 

 clusively to the bark of trees, and the whole of this divi- 

 sion of the vegetable kingdom here consists mainly of a 

 single group, Sclerolichenes, which occur in abundance 

 and in very varying types. 



Prof. Nordenskjold and Lieut. Hovgaard ascended the 

 mountain Asamajama, a still active volcano, 8,200 feet 

 high, on October 4. 



Prof. Nordenskjold has made extensive collections of 

 fossil plants from fossiliferous strata at Mogi, a fishing 

 village on the coast of Japan, and from the coal-mine 

 Takasima, both in the neighbourhood of Nagasaki, and 

 from the coal-seams at Labuan. The fossils from Mogi 

 lie in a fine white clay slate, and consist almost exclusively 

 of beautiful leaf impressions. At Takasima the fossils 

 consist principally of water plants imbedded in the 

 brownish-black shale which accompanies the coal. At 

 Labuan the fossils lie imbedded in balls of clay-ironstone 

 found in the sandy beds between the coal-seams. They 

 consist of ferns, Cycadea, and large-bladed leaf -trees, which 

 appear to have a tropic stamp, while the Mogi fossils, on 

 •the other hand, indicate a moderately warm climate. 



AN ELECTRO-DYNAMOMETER FOR 

 MEASURING LARGE CURRENTS 1 



""THE use of electric machines of large size for the 

 ■*• generation of currents of great strength has become 

 extensive, and promises to increase materially. In con- 

 nection with this, the best mode of measuring the currents 

 obtained is a matter of much importance as well as one 

 of some difficulty. 



Of the possible methods the galvanometric is probably 

 the most used, but it is objectionable as shunts of low- 

 resistance must be employed. In general, a method 

 depending upon the estimation of a very small propor- 

 tional part of the magnitude to be measured is objection- 

 able, since extreme accuracy is necessary and errors of 

 observation are magnified. The mode of measurement 

 by the electro-dynamometer is to be preferred for many 

 reasons, and it has also the advantage of being applicable 

 to to-and-fro currents, as well as to those in one direction. 

 Weber's electrodynamometer is only suitable for mea- 

 suring very small currents unless shunts are used. Trow- 



bridge has designed an electro-dynamometer through 

 which large currents may be transmitted and directly 

 measured {Proc. Am. Acad. Arts and Sci., October 9, 

 1878). This instrument works well and gives good 

 results. 



« During the past year the writer has been experimenting 

 at the U.S. Torpedo Station with an electro-dynamo- 

 meter differing from Trowbridge's in the manner of deter- 

 mining the deflective power of the current, and which 

 seems to present some advantages in simplicity and readi- 

 ness of working, while especially suitable for technical 

 use. In its general plan, particularly in the arrangement 

 by which the entire current may be passed through the 

 instrument, it follows Trowbridge's form. 



Fig. 1 is a general view of the instrument. Figs. 2 

 and 3 show the details of the suspended coil. The large, 

 fixed coils are made of thick copper ribbon. The turns 

 are insulated from each other, and the metal framework 

 is insulated from the coils. The suspension arrangement 



