544 



NATURE 



\Oct. 7, 1880 



The electric conductivity of gas-carbon and its variability 

 under pressure has been re-examined by MM. Naccari and 

 Pagliani. Carbon prisms were carefully covered at certain points 

 of their surface with copper by electro-deposition to secure good 

 contact with the wires by which they were inserted in a Wheat- 

 stone's bridge to determine their resistance. When subjected to 

 great pressures the resistances of the rods of carbon showed 

 scarcely any change. Hence it appears that the changes of 

 conductivity which carbon exhibits in the microphone and in the 

 carbon telephone under varying pressures are due not to any 

 alteration of the contact between tl'.e particles in the intimate 

 structure of the substance, but to mere changes in the external 

 contact. 



Dr. Werner Siemens has lately described to the Berlin 

 Academy a new series of experiments on the electric conduc- 

 tivity of carbon, and the way it is affected by temperature. He 

 finds that of gas retort carbon at 0° C. 0'0I36 (mercury = i), 

 and the coefficient of increase of conductivity 0*000345 P^'' 

 degree Celsius. The artificial carbon rods produced by compres- 

 sion of carbon powder also show greater conducting power with 

 increasing temperature, but the increase is not so great (as in 

 retort carbon). Dr. Siemens thinks other experimenters may have 

 been led to erroneous results by faulty connections. He effected 

 the union of the carbon ends ^^ ith the conducting wires by means 

 of galvanic coppering. The property of conducting better at 

 higher temperatures is regarded as a property of the carbon 

 material itself, not as a consequence of its structure. It may be 

 explained (Dr. Siemens says) as in the case of crystalline 

 selenium, if we assnme that the carbon is an allotropic modifica- 

 tion (containing latent heat) of a hypothetical metallic carbon. 



In his theory of the bifilar magnetometer Gauss considered 

 that the torsion of the suspending wires, and the induction of 

 the earth's magnetism on that of the suspended magnet, might 

 be neglected, as very small. In the course of several years' 

 observations, Ilerr Wild having found this to cause serious 

 discrepancy between theory and experience, has (at Pawlowski 

 Observatory) developed the theory anew, taking account of those 

 two factors. Substituting cocoon-threads for wires, he considers 

 the moment of torsion can be reduced to considerably less than 

 0'3 per cent, of the moment of gravity (it was more than 

 S per cent, with wires). The improved theory, while agreeing; 

 much better with experience, aflbrds an excellent method of de- 

 termining separately, from direct observation of the angle of 

 torsion and the three durations of vibration of the magnet in the 

 normal, reversed, and transverse position, its two kinds of 

 induction-coefficients, viz., that in (weakening, and that in in- 

 crease of the magnetic moment by induction ; also of deter- 

 mining the temperature-coefficient of magnets and of absolute 

 measurement of the horizontal intensity {Wicd. Ann., No. 8). 



It appears from recent experiments by Herr Knoblauch 

 {^Wicd. Ann., No. S) that in reflection of polarised heat-rays 

 from metals, ths rays of different heat-colours behave differently, 

 in that they have in general different angles of polarisation, pre- 

 senting, in the case of certain metals, as gold and silver, great 

 differences, and in that of others, as copper and speculum metal, 

 smaller. In the case of lead and arsenic these differences wholly 

 disappear. With the former metals the transitions in reflection 

 of different rays from linear to elliptic vibrations do not keep 

 equal pace with each other ; changing the 'angle of incidence 

 from C to the angle of polarisation, the transformation of the 

 vibration of one heat-tint is prominent, \\\\\\t in change of in- 

 cidence from 90° to the angle of polarisation, it is that of 

 another. With lead and arsenic, at all angles of incidence from 

 0° to 90°, the ellipses of certain constant heat-rays are always 

 more extended than those of the other heat colours. 



GEOGRAPHICAL NOTES 

 The full details of the Franklin Search Expedition published 

 in the iVtw York Herald of September 23 and following num- 

 bers do not contain much of scientific interest in addition to 

 what we gave last week. The narrative contains a graphic and 

 interesting account of the sledge journeys of Lieut. Schwatka's 

 party, of the various Eskimo tribes met with, of the country 

 traversed, and the remains of the Franklin Expedition. Some 

 precision is given to our knowledge of the country, and many 

 valualJe hints given as to how to brave an Arctic winter. 

 Although the extreme cold endured, 103° F. below freezing, is 

 not so great as has been experienced in one or two previous 



instances, we question whether an average temperature of 100" of 

 frost for 16 days was ever before met with. A good many in- 

 teresting relics of the Franklin party were collected, and there 

 seems no doubt that the Eskimo did at one time have a number of 

 books in a tin box belonging to the party who left the ships ; 

 but these, with gold watches and other mysteries, were given to 

 the children for playthings, and have long ago disappeared. It 

 is probable enough that among the books were some records 

 of the progress of the expedition ; but all hope of recovering 

 them may now be abandoned. We trust that there will be no 

 delay in the publication of the scientific observations which were 

 doubtless made by Lieut. Schwatka's expedition. 



The new number of the Geographical Society's Proceedings 

 provides us with an unusual supply of good readable papers of 

 moderate length. Lieut. G. T. Temple furnishes "Notes on 

 Russian Lapland," accompanied by a new map ; the Rev. W. G. 

 Lawes, the well-known missionary, "Notes on New Guinea and 

 its Inhabitants " ; the Rev. C. T. Wilson, lately of the Nyanza 

 mission, a brief narrative of a journey over new ground in East 

 Africa from Kagei to Tabora ; and lastly. Major W. M. 

 Campbell, R.E., an account of his visit to the previously 

 unknown (except from hearsay) Shorawak valley and the Toba 

 plateau, Afghanistan. The Geographical Notes supply par- 

 ticulars regarding the murder of Messrs. Carter and Cadenhead 

 in East Central Africa, and Capt. T. L. Phipson-Wybrants' 

 expedition to Umzila's country, east of Matabele-land, as well as 

 a French surveying expedition for West Africa. These are 

 followed by a rhtimi of some of Pere Duparquet's notes on 

 Orampo-land, an Egyptian exploring expedition in Somali-land, 

 M. Regel's journey in Eastern Turkestan, and a summaiy of the 

 Indian Marine Survey Report for 1S78-79. There are also some 

 useful additions to our knowledge of Eastern Perak, and an 

 abstract of a Consular report on the Chinese province of Shan- 

 tung. We must not omit to mention that the present number 

 contains the map (postponed from la^t month) of the country 

 between Sind and Candahar, showing the course of the proposed 

 railway, on which Sir Richard Temple recently lectured before 

 the Society and at Swansea. 



The new expedition despatched by the London Missionary 

 Society to Lake Tanganyika, and consisting of the Revs. A. J. 

 Wookey and D. Williams, with Dr. Palmer, left Zanzibar on 

 June 14, and crossing to the mainland at Saadaui, marched 

 thence to Ndumi. Here they remained for a few days, until 

 they got their full complement of pagti:i, and finally started for 

 the interior on June 21. Accomplishing some twelve or fifteen 

 miles a day, they reached Mpedapwa on July 14, and were most 

 kindly received by the Church Missionary Society's agents. They 

 were to recommence their journey to the lake on July 19. Their 

 caravan consists of 309 men, the chief of whom is Ulia, who 

 accompanied the Rev. Roger Price, when the bullock-waggon 

 experiment was tried some four years ago. 



From a letter in L' Exploration we learn that M. Wiener had 

 in July reached Archedona, m his exploration of the Napo, one 

 of the great tributaries of the Amazon ; unless he meets with 

 disaster, we may expect to hear of him by and by from Para. 



The Milthdhingcn of the German African Society, of which 

 six parts are published, contains much very valuable information 

 on recent exploration in Africa by German explorers. We have 

 details of the progress of Herr Schiitt's expedition in the Loanda 

 region, of Rohlfs' attempt to push southwards from Tunis, of Dr. 

 Biichner to Muata Janvo's kingdom, of Dr. O. Lenz's determined 

 and so far successful attempt to push southwards through Morocco 

 to Timbuctoo and beyond. We have, besides, records of the 

 doings of the International African Association, and of the 

 various other societies for the exploration of Africa throughout 

 the world. In the double number, 4 and 5, Dr. Reichenau 

 gives a detailed list of the collection of birds sent home from 

 Slalanga in Angola by Herr Schiitt. 



A TELEGRAM from New York, October S. states that the 

 commander of the United States steamer Alert reports the dis- 

 covery of a submarine volcano near San Alessandro, an island 

 in the Pacific. 



The eruption of the volcano Fuego in Guatemala, to which 

 we referred some weeks ago, ceased almost suddenly in the 

 second half of the month of July. M. de Thiersant, French 

 representative in Guatemala, writes to T.a Nature that another 

 volcano of the same country, Pacaya, seems inclined in its turn 

 to resume activity. At Amatitlan, a small town on the slope of 



