1829.] C 221 ] 



VARIETIES, SCIENTIFIC AND MISCELLANEOUS. 



American Dof/s. — DofS have . been 

 transported to America sinci. the second 

 voyage of Columbus ; it may even be 

 remarked, that at tiie time of his first battle 

 with the Indians of Saint Domingo, he had 

 in his little army a troop of twenty 

 bloodhounds. They were subsequently 

 employed in the conquest of ditferent parts 

 of the terra firma, particularly in Jlexico 

 and New Granada. Their race is pre- 

 served without apparent alteration on the 

 table land of Santa ¥6, where they are em- 

 ployed in stag hunting : in this they dis- 

 play extreme ardour, and still employ the 

 same method of attack wliich formerly ren- 

 dered them so formidable to the natives. 

 This method consists in seizing the animal 

 by the lower part of the stomach, and 

 upsetting it by a quick movement of the 

 head, by availing themselves of the moment 

 when the weight of the body is thrown 

 upon the fore legs. The weight of the stag, 

 thus thrown down, is frequently six fold 

 that of the dog. Some dogs of the pure 

 race also inherit, without being taught, the 

 instinct necessary for hunting the peccari, 

 in which they are employed. The skill of 

 the dog consists in moderating its ardour, 

 attacking no animal in particidar, but 

 keeping the whole herd in check, without 

 allowing itself to be surrounded. Now, 

 among these dogs, some are met ^vith which, 

 the first time they are taken into the woods, 

 make their attack in the most advantageous 

 manner ; a dog from other parents springs 

 on at once, and, whatever its strength may 

 be, is devoured in one instant. 



Law of the Phenomena attrihuted to 

 Alugnetism in motion. — From a series of 

 valuable experiments, made with discs of 

 copper, tin, zinc, and lead, 31. Saigey has 

 found that their action on a magnetic 

 needle may be thus expressed : CaUing x 

 the distance of the needle from the disc, 

 and y the number of oscillations which it 

 loses by the action of the disc, or the differ- 

 ence between the number of its oscillations 

 while oscillating alone, and while oscilla- 

 ting under the influence of the disc, and a 

 and b, two constant quantities, y= a b '— " 

 that is, the oscillations lost form a progres- 

 sion by quotients, when the distances of the 

 needle from the discs fonn a progression by 

 differences. Two numbers expressing the 

 losses are necessary for calculating all tlie 

 others, for we must determine the two con- 

 stants a and h in the formula whicli expres- 

 ses them, the first of these, a, indicating, 

 for examjtle, the loss at the unit of distance, 

 and the second, b, the quotient of one loss 

 divided by the following. The constant, u, 

 varies for difJc-rent amplitudes in the oscil- 

 lations, but the ratio, b, is invariable for all 

 amplitudes. The constants, a and b, in- 

 crease in an inverse order, not only for 

 different mctali acting on the same needle, 



but even for the same metal acting upon 

 different needles. 



Geology — The striking difference in coal 

 fields, as to inflammablg gas abounding in 

 one district and not being found in another, 

 is a matter upon which no satisfactory 

 theory has as yet been formed. In some of 

 the Newcastle coals the inflammable gas is 

 so very easily disengaged, that there have 

 been several instances where coals recently 

 drawn from the mines, and instantly 

 shipped, have, by the fall and breaking of 

 the coals descending into tlie ship's hold, 

 disengaged such a quantity of inflammable 

 gas as to ignite from the flame of a candle, by 

 which the hatches were violently blown up, 

 and the sailors severely scorched. This 

 circumstance shews how very easily this gas 

 is in some instances emitted from coal ; and 

 it must be in great abundance when we 

 know that one pound weight of some coals 

 wUl yield five cul)ic feet of this gas when 

 exposeil to fire in a retort. 



Effect of an Earthquake On 3Iarch 



30, 1828, H. M. S. Volage was lying 

 moored with two chain cables in the Bay of 

 Callao, at half-past seven o'clock a hght 

 cloud passed over the ship, at which moment 

 the noise usually attendant on earthquakes 

 in that country, resembling heavy distant 

 thunder, was heard ; the ship was violently 

 agitated, and felt as if placed on trucks and 

 dragged rapidly over a pavement of loose 

 stones. The water around hissed as if hot 

 iron was immersed in it, immense quanti- 

 ties of air bubbles rose to the surface, tlie 

 gas from which was offensive, resembling 

 rotten pond-mud ; numbers of fish came up 

 dead along side ; the sea, before calm and 

 clear, was now strongly agitated and 

 turbid, and the ship rolled about two 

 streaks, say fourteen inches, each way ; at 

 this moment the earthquake which over- 

 threw the town ensued. The A'^olage's 

 cliain cables were lying on a soft muddy 

 bottom in thirty-six feet water, and on 

 heaving up the best bower anchor to exa- 

 mine it, the cable thereof was found to have 

 been strongly acted on at thirteen fathoms 

 from the anchor, and twenty-five from the 

 ship. On washing the mud from it, the links, 

 which are matle of the best cylinder 

 wrought iron, about two inches in diameter, 

 .ippeared to have undergone partial fusion 

 for a considerable extent. The metal 

 seemed run out in grooves of three or four 

 inches long, and three eighths of an inch 

 diameter, and had formed (in some cases at 

 the end of these pfroovcs, and in otiiers in 

 the middle of them) small s])lierical luni])s, 

 or nodules, which, upon scrubbing the 

 cable to cleanse it, fell on the deck. The 

 other cable was not injured, nor did any 

 similar occurrence take place among the 

 numerous vessels then lying in tlie bay. 

 That the phenomena of earthquakci arc 



