February 20, 1891.] 



SCIENCE. 



103 



drain the whole of the south east of the country, were surveyed 

 on the scale 1:100.000: five out of the seven were ascended by the 

 traveller up to their sources. His surveys include about 4S0 m'les 

 of quite unexplored country, besides 235 miles of new work on the 

 Oyapock. Two of these tributaries carried him right into the 

 heart of the Turauc Humac Range, where he was able to study 

 the native languages. He has collected twenty-five hundred 

 words of the Oyampi language. The whole of the south east 

 region abounds in marshes, and presents a desolate picture. On 

 all sides are the ruins of Indian villages. Small-pox and dysen- 

 tery, and a steady emigration to the south-west of the country, 

 are rapidly thinning the population; so that a generation hence, 

 M. Coudreau says, the south east will be practically uninhabited. 

 The Creoles may, however, be attracted to this region on account 

 of its auriferous character, but it will not be easily exploited 

 owing to the numerous falls in the rivers. In July last the 

 travellers was about to start upon the second portion of his work. 

 He intended to navigate the Oyapock to its source, cross the 

 Tumuc Humac Mountains to the southern side, and visit the 

 Indians living near the sources of the Tapanahony by a new route. 

 Thence he will reach the Itany, descend the Aoua, and return 

 across the whole central part of French Guiana. This central 

 journey will occupy eight months. 



— A course of five lectures on the ethnology of modern Europe, 

 by Dr. D. G. Brinton, was begun Monday afternoon, Feb. 16, at 

 the Academy of Natural Sciences of Philadelphia. The subjects 

 of the different lectures are as follows : 1. '' The Predecessors of 

 Modern European Nations ; '' 2. " The Romance and Hellenic 

 Nations (France, Spain, Portugal, Italy, Greece, etc.);" 3. "The 

 Teutonic Nations (Germans, Danes, Swedes, English, etc., — Celtic 

 Eemnants);" 4. ''The Slavonic Nations (Russians, Poles, etc.);'' 

 5. " The AllophyUic Peoples (Basques, Finns, Hungarians, Turks, 

 etc.)." These lectures are free, and tickets may be obtained of 

 the secretary of the academy. Dr. E. J. Nolan. 



— In a communication to the French Physical Society, M. 

 Cailletet has described a method of connecting a metal tube or 

 stop-cock to a vessel of glass or porcelain so that the joint shall 

 be tight even under high pressures. As described in Engineering, 

 the process is simple, and consists in first coating the glass or 

 porcelain vessel with a very thin layer of platinum at the part 

 where the connection is to be made. This may be done by paint- 

 ing the glass, after slightly warming it, with a neutralized solution 

 of platinic chloride mixed with the essential oil of camomile. 

 The layer of oil and platinic chloride is then slowly heated till the 

 last traces of oU have been expelled, and the temperature is then 

 raised to a dark-red heat. The chloride is thus reduced, and the 

 platinum deposited as a bright metallic mirror on the surface of 

 the glass. On this layer of platinum a second layer of copper is 

 deposited by electrolysis, and the metal stop-cock or tube can 

 then be soldered by means of tin to this copper ring. M. Cailletet 

 states that he has found these joints to remain tight under a press- 

 ure of 300 atmospheres. 



— A theory attempting to explain the nature of the relationship 

 between the optical activity of many substances in solution, and 

 the hemihedrism of their crystalline forms, is advanced by Dr. 

 Fock, the author of the new work on chemical crystallography, 

 in Berichte, and quoted in Nature of Feb. 5. It is certainly a 

 most significant fact that all those substances whose solutions are 

 capable of rotating the plane of polarization of light, and whose 

 •crystalline forms have been thoroughly investigated, are found to 

 form hemihedral crystals; that is to say, crystals some of whose 

 Caces have been suppressed, and whose two ends are therefore 

 ■differently developed. Moreover, in those cases where both the 

 right rotatory and left rotatory varieties of the same chemical 

 compound have been isolated and examined, as in the case of 

 dextro- and Isevo-tartaric acid, the hemihedral crystals are found 

 to be complementary to each other, the faces undeveloped upon 

 the one being present upon the other, so that the one is generally 

 as the mirror-image of the other. Several ingenious attempts to 

 account for the wonderful geometrical arrangement of the 

 molecules in a crystal have been made of recent years by Bravais, 

 Mallard, and others, who developed the " Raumgitter " theory, 



and by Sohncke, who showed that all possible crystallographical 

 forms could be referred to systems of points ; yet it has been found 

 necessary by these crystaUograpbers to assume a polarity of the 

 molecule itself in order to fully explain the phenomenon of hemi- 

 hedrism. This conclusion is, moreover, borne out by the more re- 

 cent work of Lehmann upon his so-called " liquid crystals." Itis, 

 indeed, evident that hemihedral crystals owe their hemihedrism to 

 a differentiation of the various parts of the molecules themselves 

 in space. Dr. Fock assumes, for the purpose of connecting this 

 fact with the optical rotation of the dissolved crystals, the 

 tetrahedral form for the element carbon, in the most recent con- 

 ventional sense employed by Wislicenus, Van't Hoff, Victor Meyer, 

 and other exponents of the new "stereochemistry.'" The axis 

 of polarity of a molecule containing an asymmetric carbon 

 atom, will, of course, be determined by its centre of gravity and 

 the heaviest "corner" of the tetrahedron ; and Dr. Fock shows 

 that rotation of the molecule will be most easy round this axis, 

 and in the direction, right or left, determined by the relative 

 Weights of the atoms or groups disposed at the other three 

 "corners." He further shows, that, if we consider any direction 

 of vision through the solution, we must practically consider two 

 positions of the molecules, in both of which the axis of rotation is 

 parallel with our line of sight, and in one of which the apex 

 of the tetrahedron is turned towards us, and in the other is di- 

 rected away from us and the other three corners presented to 

 us. As the molecules are, of course, in rapid motion, we must 

 consider all other positions as balancing each other, and being re- 

 solved eventually into these two directions. It is then easy to 

 see, as it is now accepted from Fizeau's work that the movement 

 of molecules is capable of influencing the direction of light-waves, 

 that there must be two oppositely moving circularly polarized 

 rays produced. Now, it is generally supposed that the rotation of 

 liquids is really due to the division of the light into two circularly 

 and oppositely polarized rays, one of which, however, is stronger 

 than the other, and determines the apparent optical activity. Dr. 

 Fock completes his theory by showing the probability that there 

 would be just this difference in the amount of rotation of the 

 light in the two cases of the differently disposed molecules, those 

 with their "apices " turned towards the direction of incidence of 

 the light affecting it to a different extent from those whose 

 "bases" were the first to receive it. The theory is well worth 

 following out in the original memoir, many confirmations of it 

 being adduced from other properties of hemihedral crystals. 



— Senor Felipe Poey, the renowned Cuban philosopher and 

 naturalist, is dead. He was born in Havana, May 26, 1799, and 

 studied law in Madrid, where he was implicated in a political con- 

 spiracy, and from whence he fled to Paris. There he published in 

 1828 "La Centurie des Lepidopteres," and helped to found the 

 French Entomological Society. He returned to Havana after the 

 revolution of 1880, was commissioned in 1837 to organize a 

 museum of natural history, and became one of its directors. 

 Soon afterwards he was appointed professor of natural history in 

 the University of Havana. In 1840 he published a school geog- 

 raphy of the Island of Cuba, and in 1842 a more extensive work 

 on the same subject, and a " Geografia Universal." In 1864 he 

 published " Memorias Sobre la Historia Natural de la Isla de Cuba," 

 with Spanish, French, and Latin text. In 1865 he started a 

 monthly periodical entitled Bepertorio Fisico-Natural de la Isla 

 de Cuba, in which he described upward of two hundred and thirty 

 new species of fishes, as well as the ciguatera, or jaundice, caused 

 by eating certain Cuban fishes. He also published some remark- 

 able poems. He was a member of the Smithsonian Institution, 

 and a corresponding member of the French Academy of Sciences. 



— Some time ago M. Berthelot, judging from a text of the 

 eleventh century, formed the opinion that the word "bronze" 

 was derived from " Bi-undusium," or Brindisi. "We learn from 

 Nature of Jan. 29 that this view has been confirmed by the dis- 

 covery of a passage in a document of the time of Charlemagne, 

 where reference is made to the " composition of Brundusium : " 

 copper, two parts; lead, one part; tin, one part. It would appear 

 that at Brundusium bronze was in ancient times manufactured oa 

 a great scale. 



