159 



SCIENTIFIC SIDE-LIGHTS 



Denial 

 Depth 



ity or otherwise no longer to be ignored. 

 They occur in our drinking water, in our 

 milk-supply, in the air we breathe. They 

 ripen cream and flavor butter. They purify 

 sewage, and remove waste organic products 

 from the land. They are the active agents 

 in a dozen industrial fermentations. They 

 assist in the fixation of free nitrogen, and 

 they build up assimilable compounds. Their 

 activity assumes innumerable phases and 

 occupies many spheres, more frequently 

 proving themselves beneficial than injurious. 

 They are both economic and industrious in 

 the best biological sense of the terms. NEW- 

 MAN Bacteria, int., p. 11. (G. P. P., 1899.) 



775. DEPOSIT ON DEEP-SEA FLOOR 



The Globigerina-ooze. The globigerina- 

 ooze is perhaps the best known of all the 

 different deep-sea deposits. It was discov- 

 ered and first described by the officers of the 

 American Coast Survey in 1853. It is found 

 in great abundance in the Atlantic Ocean in 

 regions shallower than 2,200 fathoms. . . . 

 It is probably formed partly by the shells of 

 the dead Foraminifera that actually live on 

 the bottom of the ocean and partly by the 

 shells of those that live near the surface or 

 in intermediate depths and fall to the bot- 

 tom when their lives are done. 



So abundant are the shells of these Pro- 

 tozoa that nearly 95 per cent, of the globi- 

 gerina-ooze is composed of carbonate of 

 lime. HICKSON Fauna of the Deep Sea, ch. 

 2, p. 37. (A., 1894.) 



776. 



The Red Mud. 



Of all the deep-sea deposits, however, the so- 

 called " red mud " has by far the widest dis- 

 tribution. It is supposed to extend over one- 

 third of the earth's surface. It is essentially 

 a deep-sea deposit, and one that is found in 

 its typical condition at some considerable 

 distance from continental land. ... To 

 the touch it is plastic and greasy when 

 fresh, but it soon hardens into solid masses. 

 When examined with the microscope it is 

 seen to be composed of extremely minute 

 fragments rarely exceeding 0.05 mm. in 

 diameter. It contains a large amount of 

 free silica that is probably formed by the 

 destruction of numerous siliceous skeletons, 

 and a small proportion of silicate of alu- 

 mina. HICKSON Fauna of the Deep Sea, ch. 

 2, p. 39. (A., 1894.) 



777. DEPOSITS, MODERN, LIKE AN- 

 CIENT Strata Forming Now Land-building 

 under Sea. For more than two centuries 

 the shelly strata of the Subapenine hills 

 afforded matter of speculation to the early 

 geologists of Italy, and few of them had any 

 suspicion that similar deposits were then 

 forming in the neighboring sea. They were 

 as unconscious of the continued action of 

 causes still producing similar effects as the 

 astronomers, in the case above supposed, of 

 the existence of certain heavenly bodies still 

 giving and reflecting light, and performing 

 their movements as of old. Some imagined 



that the strata, so rich in organic remains, 

 instead of being due to secondary agents, 

 had been so created in the beginning of 

 things by the fiat of the Almighty. Others, 

 as we have seen, ascribed the embedded fossil 

 bodies to some plastic power which resided 

 in the earth in the early ages of the world. 

 In what manner were these dogmas at 

 length exploded? The fossil relics were 

 carefully compared with their living an- 

 alogues, anH all doubts as to their organic 

 origin were eventually dispelled. So, also, 

 in regard to the nature of the containing 

 beds of mud, sand, and limestone: those 

 parts of the bottom of the sea were examined 

 where shells are now becoming annually en- 

 tombed in new deposits. Donati explored 

 the bed of the Adriatic, and found the clo- 

 sest resemblance between the strata there 

 forming and those which constituted hills 

 above a thousand feet high in various parts 

 of the Italian peninsula. He ascertained by 

 dredging that living testacea were there 

 grouped together in precisely the same man- 

 ner as were their fossil analogues in the in- 

 land strata ; and while some of the recent 

 shells of the Adriatic were becoming in- 

 crusted with calcareous rock, he observed 

 that others had been newly buried in sand 

 and clay, precisely as fossil shells occur in 

 the Subapenine hills. This discovery of 

 the identity of modern and ancient sub- 

 marine operations was not made without the 

 aid of artificial instruments, which, like the 

 telescope, brought phenomena into view not 

 otherwise within the sphere of human obser- 

 vation. LYELL Principles of Geology, bk. i,. 

 ch. 5, p. 71. (A., 1854.) 



778. DEPTH OF EARTHQUAKE 

 SHOCK Convulsion Originates Miles below 

 the Surface. The first calculations of the 

 depth at which an earthquake originated 

 were those made by Mallet for the Neapoli- 

 tan earthquake of 1857. By means of a 

 number of lines parallel to twenty-six angles 

 of emergence, drawn in towards the seismic 

 vertical, Mallet found that twenty-three of 

 these intersected at a depth of 7y 8 geograph- 

 ical miles. The maximum depth was 8y 8 

 geographical miles, and the minimum depth 

 2% geographical miles. The mean depth 

 was taken at a depth of 5% geographical 

 miles where, within a range of 12,000 feet, 

 eighteen of the w r ave-paths intersected the 

 seismic vertical. The point where these 

 wave-paths start thickest is at a depth not 

 greater than three geographical miles, and 

 this is considered to be the vertical depth of 

 the focal cavity itself. For the Yokohama 

 earthquake of 1880. from the indications of 

 seismometers, and by other means, certain 

 angles of emergence were obtained, leading 

 to the conclusion that the depth of origin of 

 that earthquake might be between 1% and 5 

 miles. Possibly, perhaps, the earthquake 

 may have originated from a fissure the ver- 

 tical dimensions of which were comprised 

 between these depths. MILNE Earthquakes, 

 ch. 11, p. 213. (A., 1899.) 



