SCIENTIFIC TALKS.

Otago Witness, Issue 1913, 9 October 1890, Page 37

SCIENTIFIC TALKS.

By N. D. C

*** Since the introduction of dynamite by Nobel some years ago, the list of competing explosives has been regularly increasing. An invention by E. Liebert, of Berlin, is announced, which is not a rival but rather an auxiliary one, with the object of lessening the danger of thawing the dynamite when frozen, hitherto one of its chief drawbacks. To attain this he adds a chemical the freezing point of which is 35deg Fahr. below zero, so that the compound with dynamite is much less liable to freeze than the explosive itself, which becomes frozen at the comparatively high temperature of 40deg. This additional constituent, it is said, does not impair the explosive force. If the invention fulfils the expectations held regarding it, it should prove an important one in those countries where the winter climate is severe. ' * # * In Professor Dana's new work on the Hawaiian volcanoes we have the benefit of his scientific attainments combined with a practical knowledge of the region mentioned, for the great American scientist was attached to the United States expedition which explored these islands in 1840. He gives the domes of these volcanoes world-wide precedence in size, for although their height above sea-level is only 14,000 ft, the base from which they rise lies 14,000 ft to 18,000 ft beneath the sea. They are singular also in the great fluidity of their lava, which wells up and flows along — not explosive like the Vesuvian and other eruptions, including that of our own Tarawera, shooting forth ashes, stones, and bombs. The range of volcanic action extends for 400 miles in two lines, probably of fault or fissure, and nearly parallel. There seems to be no connection in point of time between the action of the two craters, Mauna Loa and Kilauea, on the same mountain, but with a cifference of 10,000 ft in level and some 20 miles apart. The latter volcano is not to be confused with Krakatoa, in the Stiaits of Sunda, with which we all are or should be familiar, as the one which caused such a terrific upheaval in 1883, and the clouds of dust from which were believed to cause the beautifully strange sunset and twilight effects. Kilauea is the volcano which Dana has previously mentioned as being active every period of eight or nine years — the time taken by the lava to rise a certain amount within the crater. It is on this mountain that the thin threads of volcanic glass are found which the natives have named after one of their goddesses " Pele's hair." *** Not long agoM. Pasteur was practically the undisputed chief in the domain which he hadv-made particularly his own. Universal admiration rewarded him for his researches in regard to hydrophobia and its prevention or cure. Lately a change has taken place, and not only the value of the statistics of the anti-rabic treatment but the method itself has been impugned. It would be presumptuous at this distance to express an opinion as to the value of the former, the more so as the indecisiveness of figure duels receives abundant local illustration. To give one instance, however : in the Department of the Seine for the four years preceding the Pasteurian treatment there were 38 deaths, and for the four succeeding years 37. As to the method itself, it is commonly taken for granted that it is the same as vaccination for smallpox ; and if good for that, why not for rabies 7 But, say the opponents of the system, this is not so ; the two methods are totally unlike. In vaccination, as practised, an attenuated or weak form of the disease is used to inoculate the healthy patient. The cells in the blood which meet the invaders overcome them in their weak state, and when in turn the virulent disease comes the way of the individual it proves comparatively harmless. Now the Pasteurian method is the reverse of this ; the patient, bitten by the rabid animal, received into his system the disease of the most virulent type, and is thereafter inoculated with the weakened form. Dr Gibier, a disciple of the illustrious Frenchman, in an article in the North American Review, which can be taken as a reply to the attack on the system, points out that the period of incubation of the disease is usually over three weeks, and that the patients if taken in time are benefited before it has had time to develop. This view appears to be endorsed by the bulk of English scientific opinion. Perhaps the weakest point in the Pasteurian method is the admitted changes which have been made in the strength of the virus, so that the impression cannot be avoided that even yet the experimental stage has not been passed. *** How often have we heard of the tropical climate of the carboniferous or true coal period, its warmness and humidity, and even an atmosphere laden with carbonic acid, which had all contributed to the luxuriant forest growth which was to form the coal seam ot the fufcuie. But a new theory is placed before us by Dr Neumayr, who points out that it is not to the tropics that we must look for extensive coal beds, but that the great coal countries are America and China, in neither of which does the coal reach the thirtieth parallel of latitude, and the same is true of the Buiopean countries. The reason of the absence of carbonaceous beds is nothing else than the high temperature, which so quickly promotes decay. More remarkable still, in seeking for the vegetation of the present day allied to the carboniferous flora, we are directed not to the tropics but to the moors of temperate and sub-arctic zones. This kind of formation, although acknowledged, has hitherto been looked on as presenting a less striking analogy to the true coal period than the mangrove forests, such as the everglades of Florida, whose impenetrable swamps are known only as the haunt of the alligator and wild fowl. Northwards the coal deposits range to the American polar archipelago, Rpitzbergen, and Nova Zembla, and the anomaly of a uniform climate from the equator to the poles, previously required, is thus disposed of, for only a slightly warmer climate than their present one is needed for this plant life. The absence of the carboniferous flora from the tropics, its first appearance being in the sub-temperate zone of South Brazil, is entirely in favour of this

view, while the distinct nature of the ooal flora of South Africa, India, and Australia is a further argument against the uniform climate theory. A strange feature of these latter coal areas is that the contemporary strata give evidence of ice action which, although inconclusive, is yet much more in accordance with the prevalence of a cold than a tropical temperature.