﻿240 Scientific Intelligence. 



as associated with hypersthenyte, lherzolyte, and granite ; the dia- 

 base as aphanitic, or microcrystalline, porphyritic, amygdaloidal, 

 or chrysolitic, and by alteration becoming gabbro rosso, and 

 variolitic and uralitized diabase. He observes that these rocks 

 occur in close association, the diabase forming the upper portion 

 of an ophiolitic mass, and the euphotide in intercalated beds or 

 masses; and that the serpenti nous change has often penetrated 

 into the enclosed argillaceous sedimentary beds of the Eocene ; 

 that the idea of a pre-Eocene age, assumed by some, is wholly op- 

 posed by the facts. In the amount of alteration, the region dif- 

 fers from the Scotch and Irish described by Mr. Judd ; and the 

 eruptions in Italy were submarine instead of subaerial. 



From numerous observations it is shown that the euphotide 

 and diabase are parts of the same eruptive magma, and that the 

 former is simply a result of slower cooling, becoming true gran- 

 itoid in texture in the deeper portions of the originally liquid 

 mass. 



Signor Lotti says that in Italy the term gabbro cannot be used 

 for a labradoritic euphotide, as now common in lithology, be- 

 cause it retains there its original use for a serpentine rock, gabbro 

 verde being the unaltered and gabbro rosso the altered and red- 

 dened. This fact is enough to condemn the term to banishment 

 from science. j. d. d. 



V. Onus probandi left for others. — The leaving of the onus 

 2irobandi for others is no uncommon occurrence in science. But 

 it has recently been dignified by being presented as a worthy 

 geological method by a distinguished English geologist on a 

 prominent occasion. He opens his discussion, and confidently ends 

 it, with the sentiment that " while admitting the possibility of 

 these identifications [those of schists and gneisses with any of 

 the strata of Palaeozoic or later age] the evidence in their favor 

 has been in so many instances proved to be fallacious that the 

 onus probandi lies on him who asserts, not on him who denies 

 the identification." This means that, in cases of doubt, one side 

 may be assumed to be true by the self -convinced geologist until 

 the other has been proved true by somebody else. It is a method 

 of dealing in science that is likely to turn out disastrous, not to 

 truth, for others will investigate, but to the positivist who finds 

 comfort in his truth however much he may think himself sus- 

 tained by "all the rules of evidence and reasoning." The same 

 memoir says, in another place : " all attempts to identify large 

 groups of metamorphic rocks with strata of post-Archgean age 

 have proved to be failures." So Professor Bonney thinks. The 

 really progressive geologist — not of " the new school in geology" 

 of and for which he speaks — would reverse this statement and 

 say : The identification of all large groups of metamorphic rocks 

 with strata of Archaean age has not yet been accomplished. This 

 is the precise fact. 



Again he says: "It will surprise me if the comparatively late 

 date assigned by some geologists to the marble of Carrara proves 



