Feb. 22, 1872] 



NATURE 



529 



sciousness, and vice versa, quickly, almost instantaneously, 

 and many persons habitually do so. But the transition 

 period is sometimes prolonged, and stages are observable. 

 The first thing that occurs is the lowering, or cessation, of 

 that control over the mental processes which is the highest 

 of our powers, the one requiring the greatest effort, and 

 the one most easily lost. In this condition the thoughts 

 ramble unchecked, chase one another confusedly over the 

 mental field, and give rise to all sorts of incongruities of 

 the imagination. At the same time, Ijeing unrestrained, 

 they are excited, and evince efforts of memory and even 

 of combination, of which, in the regulated state of wake- 

 fulness, they are quite incapable. In this way the images 

 of persons and places " events, and items of knowledge, 

 long forgotten in the ordinary state, are recalled with 

 distinctness, and we fancy that new information has been 

 acquired when it is only forgotten facts that are recalled. 

 He did not agree with the physiologists who conceive 

 that dreaming depends upon an inequality in the condi- 

 tion of different parta of the brain, some being excited or 

 wakeful, while others are quiescent or asleep. He rather 

 took the view that all the parts of the cerebral hemispheres 

 combine in each of the efforts of control, consciousness, 

 memory, and other mental acts, that all suffer alike from 

 those efforts, alike need the restoring changes which take 

 place in sleep, and, xo%<t\htr, pari passu, pass through the 

 stages on the way to and from sleep, in which dreaming, 

 sleep-walking, &c., occur. 



NOTICE OF THE ADDRESS OF PROF. T. 



STERRY HUNT BEFORE THE AMERICAN 



ASSOCIATION A T INDIANAPOLIS * 

 T N a brief notice of the recent address of Prof. Hunt, 

 ■'■ it is stated that, while the discussions show learning and 

 research, and his review of the progress of opinions with 

 regard to the Taconic and associated rocks is an able 

 presentation of the subject, its conclusions are through- 

 out open to doubts and objections. Since it is fairer to 

 an author to make special, rather than general, criticisms, 

 I propose to state here a part of the objections referred to 

 in that remark. They ate as follows : — 



I. That, while accepting the ordinary views with regard 

 to most " pseudomorphs by alteration" (crystals chemi- 

 cally altered without a loss of form\ he rejects them with 

 respect to those that are silicates in composition ; that is, 

 he denies that the crystals of serpentine having the form 

 of chrysolite, pyroxene, dolomite, &c.,are pseudomorphs ; 

 and the same of those of steatite, having the form of 

 hornblende, pyroxene, spinel, &c. ; of those of pinite hav- 

 ing the form of nephelite, scapolite, S:c. ; and so in other 

 cases ; — notwithstanding that (1) they bear positive evi- 

 dence of change in having ordinarily no polarising 

 properties, and no other interior features or qualities con- 

 forming to the external form ; that (2) the crystalline 

 forms are just those presented by the species after which 

 they are supposed to be pseudomorphs, and the idea of 

 their being real forms of a single polymorphous species is 

 wholly inadmissible, as pronounced by every crystallogra- 

 pher who has written on the subject ; that (3) the pseudo- 

 morphs show all stages in the process of change from in- 

 cipient to complete alteration, in the latter case not a trace 

 of the original mineral remaining. 



In this assumption, for it is little better, he opposes the 

 views of every writer on pseudomorphs, excepting one — 

 Scheerer ; and Schcerer's chemical speculations, which 

 are at the basis of his opinions, he rejects, like all other 

 chemists. 



This unwarranted assumption has a profound position 

 in the system of views on metamorphism which Prof. 



* Prof. Hunt's address has been published in the "American Naturalist" 

 for September, 1871, and, since then, in part, in Nature, Vol. v. Nos. 105, 

 106. 107. Prof. Dana's reply is reprinted from advance-sheets of SUliviaJt's 

 yourttal iorw^rAid to us by the author. 



Hunt holds, and gives shape and intensity to his opinions 

 of the views of others. 



2. That, in commencing a paragraph with the sentence, 

 " The doctrine of pseudomorphism by alteration, as taught 

 by Gustaf Rose, Haidinger, Blum, Volger, Rammelsberg, 

 D.ana, Bischof, and many others (meaning thereby other 

 writers on pseudomorphism), leads them, however, to 

 admit still greater and more remarkable changes than 

 these, and to maintain the possibilityof converting almost 

 any silicate into any other"— he grossly misrepresents 

 the views of at least Rose, Haidinger, Blum, Rammels- 

 berg, Dana ; and that he completes the caricature in the 

 closing sentence of the same paragraph, in which he says, 

 " In this way we are led from gneiss or granite to lime- 

 stone, from limestone to dolomite, and from dolomite to 

 serpentine, or more directly from granite, granulite or 

 diorite to serpentine at once, without passing through the 

 intermediate stages of limestone and dolomite ;" part of 

 which transformations, 1, for one, had never conceived ; 

 and Rose, Haidinger, Rammelsberg, and probably Blum 

 and the " many others," would repudiate them as strongly 

 as myself Next follows a verse from Goethe, that is made 

 to announce his personal vexation with their " sophistries ;" 

 alias absurdities, as the context implies. 



Prof Hunt's rejection of established truth alluded to 

 under sec. I here manifests its effects in leading him to 

 misrepresent— although unintentionally — the views of 

 writers on pseudomorphism ; and to add to his misrepre- 

 sentation by means of the strange conclusion, that, because 

 such writers hold that crystals may undergo certain 

 alterations in composition, therefore they believe that 

 rocks of the same constitution may undergo the same 

 changes ; as if it were not possible that external or epi- 

 genic agencies might reach and alter crystals under some 

 circumstances of position, when they could not gain 

 access to great beds of rock. Haidinger, the eminent 

 crystallographer, mineralogist, and physicist of Vienna, 

 and one of the most prominent writers on pseudomorphism, 

 never wrote upon the subject of the alteration of rocks at 

 all, and this is true of others, against whom the above 

 charge is made by Mr. Hunt. 



With a little clearer judgment, part at least of that 

 vexation of spirit which required the help of a great Ger- 

 man poet, and the German language, adequately to ex- 

 press, might have been avoided. 



3. That he charges me with the opinion of Bischof, that 

 " regional metamorphism is pseudomorphism on a grand 

 scale :"' when I make no such remark, neither express the 

 sentiment, in my Mineralogy of 1S54, in which I give an 

 abstract of Bischol's views and make my nearest approach 

 to them ; and when, if there was any occasion for a notice 

 of my opinions, a critic of 1871 should have referred to 

 the formal expression of them in my " Manual of Geology," 

 first published in 1863. The reader will there find the 

 " diagenesis " of Giimbel, which Mr. Hunt takes occasion 

 to commend, applied, as had been done by others, 

 although Giimbel had not then announced it ; and also 

 other points discussed, with but a brief allusion to 

 pseudomorphism. 



The above remark by Mr. Hunt is not made with special 

 reference in his address to magnesian silicates, or any 

 other particular class of siliceous minerals ; but, as the 

 context shows, to rocks in general. I have held to views 

 respecting the origin of serpentme which Prof Hunt re- 

 jects, and have sustained them on the ground that the 

 pseudomorphous crystals of serpentine show what trans- 

 formations are chemically possible, and that hence they 

 may possibly illustrate the changes which beds of rock 

 have undergone. I have not applied this principle in 

 accounting for the origin of ordinary metamorphic rocks, 

 because, as above observed, crystals may often be reached 

 by agencies which can never reach or aft'ect rock-forma- 

 tions, and for various other reasons against it. But the 

 case of serpentine has been regarded as somewhat 



