December 28, 1893] 



NA TURE 



207 



length and section of the steel, it is possible to arrange that the 

 two residual magnetisms shall just neutralise each others effect 

 in the air gap. A rather novel method was employed to 

 measure the current. A small rectangular tunnel was made in 

 an ebonite plate, placed between the pole-pieces of the electro- 

 magnet, connecting two large flat cylindrical vessels, one of 

 which communicated with an almost horizontal glass tube. 

 Electrodes were fixed on opposite sides of the tunnel, at the 

 part of the field it was required to measure, so that a current 

 could be passed across the tunnel. Under these circumstances, 

 when there was a magnetic field between the pole-pieces, on 

 passing a current between these electrodes and through 

 the mercury, the mercury tended to flow from one of the 

 cylinders to the other. A little alcohol placed above the 

 mercury in the one cylinder flows along the inclined tube, and 

 by its position indicates the pressure exerted by the mercury. 

 The current through the mercury being constant, the pressure is 

 proportional to the strength of the field. The authors say that 

 by the above means it is possible to obtain visible readings for 

 minute variations of the field, whether it be strong or weak. 



In the Proceedings of the Boston Society of Natural History, 

 vol. xxvi. July, 1893, we note that Mr. Warren Upham re- 

 asserts his theory of the formation of drumlins in the neighbour- 

 hood of Boston. He now brings forward as confirmatory evi- 

 dence the occurrence of deflected glacial striae in Somerville, 

 north-west of Boston. Mr. Upham's theory, which was fully 

 expressed a year ago (Proc. B.S.N.H. vol. xxvi. December, 

 1892), supposes a rapid accumulation of the drumlins taking 

 place during a period of rapid melting of the ice-sheet. Such 

 periods were episodal occurrences, followed temporarily by re- 

 advance of the ice or cessation of its melting ; they mark the 

 oscillatory nature of the influences which brought about the final 

 recession of the ice from these areas. The material forming 

 the drumlins was primarily collected by the ground-ice carried 

 upwards through the ice-sheet as a result of the differential 

 velocities of flow in the superficial and ground-ice. It became, 

 after tracing a steep parabolic curve, part of the super-glacial 

 drift, and began then a slowly descending movement, owing to 

 surface-melting during the retreat of the ice. As the super- 

 ficial drift was washed onwards and downwards over the melting 

 ice, it was gradually transformed into true till. If now an ad- 

 vance of the ice-sheet took place, the super-glacial and englacial 

 drift would be caught between a more rapidly-moving upper 

 current of ice and a thin lower stratum of slowly-moving ice. 

 The drift would suffer, therefore, from shearing movements, and 

 be gathered into great lenticular masses, or sometimes long 

 ridges, of drumlins, probably farther altered and added to before 



I their final exposure. These are the main arguments of Mr. 



P Upham's theory, to several of which grave objections have 



already been made by Prof. Davis, Mr. G. H. Barton, and 

 others. 



In Feter7nami's Mitleilungen, November, 1893, a coloured 

 map is published in illustration of Sir Thomas Elder's Austra- 

 lian Expedition of 1891-92. The map is reduced from the 

 original to scale r : 3,000,000. The routes of travel, the sta- 

 tions at which the various observations were taken, and the 

 geographical features of the country traversed, are all fully 

 entered. The editor gives a brief statement of the objects of 

 the expedition and its attendant success (pp. 269-270). 



A WRITER in "Insect Life" (vol. vi. No. i.), issued by the 

 U.S. Department of Agriculture, describes a remarkable ex- 

 ample of mimicry by a spider. At Jamesburg, N.J., in August 

 of this year, his attention was drawn to what was apparently a 

 gall, perfectly formed, and growing upon the upper surface of 

 a leaf of a small oak tree. On handling the leaf, however, 

 NO. I 26 I, VOL. 49] 



the supposed gall rolled off, and when it was picked up 

 was found to be in reality a spider {Ordgarius Cornigerus^ 

 Hentz) which had been resting on the leaf, its curiously 

 formed abdomen simulating exactly both in form and colour 

 the common oak gall, even to the tiny punctures through 

 which the gall insect makes its exit when mature. 



GusTAV EiSENhas commenced the description of the earth- 

 worms of California ; though a dry and rainless country for six 

 months in the year, it still would seem to possess a worm fauna 

 rich both in species and individuals. With the exception of 

 two very imperfectly described species by Kinberg, no true earth- 

 worms have been recorded from this part of the world. While 

 reserving a detailed account for the Transactions of the Cali- 

 fornian Academy, Mr. Eisen gives diagnoses of Deltania, a new 

 genus near Microscolex, with three new species ; D. elegans 

 (pretty widely diffused, and the largest species of the genus, 

 being from two to four inches in length) ; D. troyeri (from 

 Golden Gate Park, San Francisco) ; and D. benhami (Alameda 

 County). Argilophilus is a new genus near Plutellus ; A. 

 ornatus, n. sp., is the most common earth-worm of the region, 

 aud A. papilli/ei; n. sp., is a more southern form. (Zoe for 

 October, 1893, vol. iv. p. 248.) 



The current number of Danckelmaus Mittheilungiu con- 

 tains an account of an exploring trip made to the upper regions 

 of Togo, between the years 1890 and 1892, by Captain E. 

 Kling and Dr. R. Biittner. Copious extracts from Captain 

 Kling's diary of his journey are given, with sketches of the 

 features, tattoo marks, and head-dresses of the various tribes of 

 natives he met with ; there is also figured a hobby-horse played 

 with by the children, which was made from a strong stalk of 

 millet (in the drawing it looks like a bamboo cane), the head 

 of a horse with ears and bridle being carved out of the root. 

 Very extensive collections of the natural history of the countries 

 visited were made, and astonishingly complete details, consider- 

 ing the time that has elapsed since the specimens were received 

 in Berlin, are given. The lists of the mammals, reptiles, and 

 amphibia of the Togo district are by P. Matschie, the birds of 

 the environs of Bismarckburg are named by Dr. Ant, Reiche- 

 now, the fish and Crustacea by Dr. F. Ililgendorf, the moUusca 

 by Prof. E. Martens, the insects by Drs. H. Stadelmann and 

 F. Karsch and H. J. Kolbe, the worms by A. Collin. The 

 collection of plants has been only in part worked out, about 

 560 flowering plants species of were found, and a small number 

 of ferns, lichens, and fungi. In a series of thirteen plates made 

 from photographs taken by Dr. R. Biittner, there are views of 

 Bismarckburg, of the natives of Adeli, Bimbila, &c. With 

 investigations like these in addition to those pursued by our own 

 countrymen, the tropical parts of Africa will soon be better 

 known than the northern regions of the continent which lie 

 within the sight of Europe. 



The order of the Laminariaceae is one of the most distinct 

 and well defined among the Phaeosporeas, the members of this 

 order of sea weeds are all of comparatively large size, while 

 the species of Macrocystis reach a length, even surpassing that 

 of some tropical "climbers," and those of Lessonia possess 

 stems which in appearance resemble the trunks of some trees. 

 Since the date (1848) of J. G. Agardh's " Species Algarum " no 

 attempt has been made to classify the numerous genera of this 

 order, but in a very interesting memoir on the classification and 

 geographical distribution of the Laminariaceas, by W. A. 

 Setchell, which appears in a recent number of the Transactions 

 of the Connecticut AcaJemy (vol.ix, 1893), we find the order 

 divided into three tribes : I, Laminariideje, with (i) Lamin- 

 arieae, containing the three genera. Chorda, Saccorhiza, and 

 Laminaria ; (2) Agareae, with Agarum, Thalassiophyllum, 

 Costaria, Cymathaere, and perhaps Arthrothamnus. II. Les- 



