458 Queries aiid Observaliotis, 6^c. 



of basalt into clay, or sand, will be consistent with this mode of 

 formation. Many of the solutions containing terrene matter 

 might be erupted at a boiling temperature, like the siliceous 

 water thrown out of the hot springs in Iceland, and on cooling 

 they might deposit their contents, the matter from each eruption 

 forming a separate layer or stratum *. 



In some parts of the earth the quantity of matter throv\'n out 

 during one eruption may have been sufficiently great to admit 

 the crystallization of wlwle groups of mountains. In other in- 

 stances it may have been so widely diffused as to form very thin 

 strata. And here it may be proper to remark, that different 

 beds and strata are not arranged in nature in the order of their 

 specific gravity; the lowest are not aiways the heaviest, neither 

 are they arranged according to their more perfect crystallization; 

 tor, though generally the lower rocks are more crystalline than 

 4he upper, we not unfrequently find some of the upper strata 

 more perfectly crystalline than the subjacent rocks. Now if the 

 matter of which the upper and lower rocks are formed had been 

 oo-existent in the same fluid medium, one or other of the above 

 effects must have taken place ; but if each stratum were formed 

 by a separate eruption and deposition, they might vary both in 

 specific gravity and degrees of crystallization, without any regard 

 to the order in which they were deposited f. 



In endeavouring to trace the causes of very complicated pliae- 

 noraena, those explanations are to be preferred which apply to 

 the greatest number of cases, and are consonant with existing or 

 analogous facts. Now I conceive that the alternation of aqueous 

 and igneous eruptions offers a more satisfactory explanation of 

 the formation of rocks than any that I am acquainted with. At 

 the same time it assigns an office to the immense craters and 

 fractures which have once perforated or intersected the globe. 



It is an acknowledged maxim, that Nature, or to speak more 



* To compare great things with small, there is an analogous formation 

 taking place every day in the channels which receive the boiling wat4Ers from 

 some of the steam-cnsjines in the county of Durham. This water contains 

 a large quantity of earthy matter which is deposited every day, except Sun- 

 <lay, in regular layers that may be distinctly counted, with a marked line 

 for the interval of repose on Sunday, between each week's forniation: 

 hence the stone got out of these cijannels has received fro«n the country 

 people the name oi Sunday stone. 



i' By considering each stratum as a local formation, we are relieved from 

 the difficulty of accounting for the disappearance of the vast beds of sand- 

 atone and chalk, with all tlve upper strata, in countries where they arc not 

 found at present. Could we be presented with an accurate delineation of 

 the elevations and depressions of the earth's surface, sufficient vestiges of 

 its ancient physical geography might still remain to enable us to trace some 

 •«f the great basins, or lukcs, in which the sejiai ate formations of the upper 

 fctrata took place. 



correttly 



