Mr. Darwin on the Formation of Mould, 89 



the bitumen oozes up from the bottom, and above it the well is filled by 

 a spring of clear, cool, and tasteless water. No bubbles of gas were 

 observed to be given out by the bitumen. About forty barrels are 

 produced here annually. 



From the different situations in which bitumen is produced, and 

 from there being nothing in the composition of either the tertiary or 

 secondary rocks to account for its production, as well as from its 

 rising where there has been a great dislocation of the strata j the 

 author is induced to infer that it is derived from the region of volcanic 

 action, which may be almost demonstrated to underlie the Ionian 

 islands. On the northern coast there is another mineral spring, which 

 rises on the line of a considerable fault in the Apennine limesioae, 

 about half a mile to the north of the junction of tlie tertiary and se- 

 condary rocks. It consists of turbid water, resembling diluted milk 

 in appearance, and issuing at the foot of the cliffs, flows on the surface 

 of the sea- water, in a stratum a few inches thick. Flakes of a slimy 

 white substance abound in this water, and may be seen floating in 

 the sea for a considerable distance. A strong smell of sulphuretted 

 hydrogen is diffused around. The spring indicated a temperature of 

 65°, which is near the mean temperature of the latitude of Zante. 

 Thi^, therefore, cannot be reckoned among thermal springs, though 

 from its close resemblance to the mineral waters of many volcanic 

 regions, as the Aquae Albulae near Rome, its origin may be referred 

 to some analogous cause. 



A paper was afterwards read " On the Formation oi Mould," by 

 Charles Darwin, Esq., F.G.S. 



The author commenced by remarking on two of the most striking 

 characters by which the superficial layer of earth, or, as it is commonly 

 called, vegetable mould, is distinguished. These are its nearly homo- 

 geneous nature, although overlying different kinds of subsoil, and the 

 uniform fineness of its particles. The latter fact may be well ob- 

 served in any gravelly country, where, although in a ploughed field, a 

 large proportion of the soil consists of small stones, yet in old pasture- 

 land not a single pebble will be found within some inches of the sur- 

 face. The author's attention was called to this subject by Mr. Wedg- 

 wood, of Maer Hall, in Staftbrdshire, who showed him several fields, 

 some of which, a few years before, had been covered with lime, and 

 others with burnt marl and cinders. These substances, in every case, 

 are now buried to the depth of some inches beneath the turf. Three 

 fields were examined with care. The first consisted of good pasture 

 land, which had been limed, without having been ploughed, about 

 twelve years and a half before : the turf was about half an inch thick ; 

 and two inches and a half beneath it was a layer or row of small aggre- 

 gated lumpsof the lime forming, at an equal depth, a well-marked white 

 line. The soil beneath this was of a gravelly nature, and differed very 

 considerably from the mould nearer the surface. About three years 

 since cinders were likewise spread on this field. These are now buried 

 at the depth of one inch, forming a line of black spots parallel to 

 and above, the white layer of lime. Some other cinders, which 

 had been scattered in another part of the same field, were either still 



Phil, Mag, S, 3. Vol. 12. No. 71. Suppl. Jan. 1838. N 



