UC-NRLF 
 
AMERICAN GEOLOGY. 
 
 LETTER 
 
 ON SOME POINTS OF THE GEOLOGY OF TEXAS, 
 
 NEW MEXICO, KANSAS, AND NEBRASKA; ADRESSED TO 
 
 MESSRS. F. B, MEEK AND F. V. HAYDEN. 
 
 BY 
 
 JULES MARCOU. 
 
 ZURICH 
 
 PRINTED FOR THE AUTHOR, BY ZURCHER & FURRER. 
 
 1858. 
 
MATTHEW LIBRAKY 
 
Letter on some points of the Geology of Texas, New 
 Mexico, Kansas, and Nebraska; adressed to Messrs. 
 F. B. Meek and F. V. Hayden. 
 
 Zurich (Switzerland), October 20th 1858. 
 Dear Sirs: 
 In April last, I received the following letter: 
 
 Smithsonian Institution. 
 Washington, D. C. March 24th 1858. 
 Dear Sir, 
 
 Inclosed I send you a copy of the Geological results arrived at 
 from an Exploration of the Black Hills of Nebraska. I am quite cer- 
 tain it will interest you much and you will do Mr. Meek as well as 
 myself a great favor by securing its insertion in some journal in your 
 country, or in France. 
 
 Believe me very truly your obedient servant 
 
 M. Jules Marcou, Prof. F. V. HAYDEN. 
 
 Zurich (Switzerland). 
 
 It was accompanied by the following note from my friend 
 Prof. Spencer F. Baird, assistant-secretary, Smithsonian In- 
 stitution : 
 
 March 24th 1858. 
 My dear Sir, 
 
 I send a communication from Dr. Hayden which he wishes com- 
 mended to your favorable consideration. 
 
 Yours truly 
 
 Prof. J. Marcou. g. p. BAIRD. 
 
 I accordingly translated your short memoir and procured 
 its publication in the Bibliothdque Universelle de Geneve; as it 
 appeared in the National Intelligencer and in Sillimaris Journal, 
 I will not reproduce it here. 
 
 Not having the honor of a personal acquaintance with 
 you, I considered this communication as a proof that, after 
 having opposed my opinions and observations on the Geology 
 of the West, you had changed your views and found that my 
 observations, or hazardous guesses, as they are called in Sil- 
 
 967541 
 
4 AMERICAN GEOLOGY. 
 
 limarfs Journal, were not so absurd after all , and I gave to the 
 article published in the Bibliothdqm Universelle de Geneve, Juin 
 1858 (Note* pour servir d une description ge'ologique des Montagues 
 Rocheuses) a direction showing that change in your opinions, be- 
 lieving candidly that such was the meaning of your message. 
 From subsequent letters it appears this was not the case, and 
 now it is my duty to give a few words of explanation, that 
 no mistake may arise from what has occurred. 
 
 In your letter dated Washington May 30th 1858 you say: 
 I hope you will permit me respectfully to suggest, that I cannot 
 agree with you in your conclusions respecting the Pyramid Mount 
 section (see: Geology of North America , p. 18). By this I mean to 
 say, that I regard all the beds of that section down at least to A. 
 as Cretaceous. The beds below may be Jurassic or Triassic, 
 though I know of no evidence that they are so. Notwithstanding 
 the high authorities you have for regarding the Gryphcea and 
 Oslrea found at Pyramid Mount as G. dilatata and O. Marshii, 
 I feel quite confident from collections shown to me from the 
 South West , that these fossils are at some places associated 
 with well marked Cretaceous forms; while numerous facts 
 point to the conclusion that the bed from which you obtained 
 these fossils at Pyramid Mount, is equivalent to N 2 of our 
 ((Nebraska section, in which we find Baculites and other Cre- 
 taceous fossils. In addition to this , all the facts in our pos- 
 session respecting the rocks in Kansas and south to the Ar- 
 kansas river, point directly to the conclusion that the sand- 
 stones of our N 1 in Nebraska , in which the leaves already 
 ((mentioned occur, are represented by the beds B., C. , and 
 D. of your Pyramid Mount section; while the beds from which 
 Dr. Hay den obtained the Jurassic fossils near the Black Hills 
 hold a position far beneath these. 
 
 I respect your opinion , gentlemen , but I beg you to allow 
 me to continue to regard my observations and conclusions as 
 exact. I would also say that I do not understand the value of the 
 following phrase in a note to your memoir entitled: Descrip- 
 tions of New organic remains, collected in Nebraska Territory 
 
AMERICAN GEOLOGY. 5 
 
 in the year 1857; by Dr. F. V. Hayden, Geologist to the Ex- 
 ploring Expedition under the command of Lieut. G. K. Warren, 
 Top. Engineer U. S. Army; together with some remarks on the 
 Geology of the Black Hills and portions of the surrounding country ; 
 pag. 47 : By these remarks we do not wish to withhold from 
 Mr. Marcou the credit justly due him for having first suggested 
 the existence of Jurassic rocks in this region ; for you know 
 perfectly well that my conclusions as to the existence of the 
 Jurassic rocks in the Black Hills and the Yellow Stone river 
 region, were based upon my observations at Pyramid Mount, 
 and if I made a mistake there, I cannot claim any credit for 
 arriving at the truth , by taking for my starting point an error 
 so enormous as you think I have committed in the geology 
 of the Tucumcari Mounts. 
 
 In your memoir entitled : Remarks on the Tertiary and Cre- 
 taceous formations of Nebraska , and the Parallelism of the latter 
 with those of other portions of the United States and Territories; 
 I find page 18, the following note: We think these (Marcou's 
 G. dilatata and 0. Marshii) identical with species found by 
 Dr. George G. Shumard at Fort Washita, Texas, where they 
 appear to hold the same geological position, and are asso- 
 ciated with Ammonites vespertinus Morton. Dr. B. F. Shumard 
 has correctly, as we believe, referred the first to Gryphcea 
 <iPitcheri Morton, and described the latter as a new species, 
 under the name of Ostrea subovata (see : Capt. Marcy's Re- 
 port Explorations Red river, page 205. Appendix E; Pale- 
 ontology). 
 
 Supposing that your rejection of my conclusions , with 
 regard to the Jurassic rocks of Pyramid Mount, was entirely 
 based on my determination of these fossils, and thinking it 
 possible you might change your mind in reading the chapter 
 on Paleontology in my Geology of North America, which I have 
 since sent to you; in my answer to your letter of 28th May 
 I begged you to tell me if you still continued to hold the 
 same views on that subject. You were kind enough to reply 
 in the following manner: We also still think the shell you refer 
 
6 AMERICAN GEOLOGY. 
 
 to Gryphcea dilatata var. Tucumcarii, is the true G. Pitcheri 
 Morton, and the oyster you refer to 0. Marshii, we think 
 the same as 0. subovata of Shumard. Dr. Geo. G. Shumard 
 says : G. Pitcheri (meaning the true Pitcheri of Morton) ranges 
 through the whole series of the Cretaceous formations of Texas 
 and New Mexico (see: Trans. St. Louis Acad. Sc., vol. I, NO 2, 
 p. 289): all the other explorers of that region I have seen 
 tell me the same. You will bear in mind Dr. Shumard in 
 speaking of G. Pitcheri, refers to the peculiar form you re- 
 ft gard as G. dilatata, which you may see is exactly the type 
 of the original G. Pitcheri figured by Morton. The shell you 
 and Ferdinand Roemer figured as G. Pitcheri is now regarded 
 by all in this country who have given much attention to the sub- 
 ject, as a distinct, and unnamed species. 
 
 I will answer your objections as briefly as possible and 
 try to be clear and precise in my meaning. 
 
 First. I would say that, before coming to a final conclu- 
 sion with regard to the determination of the Gryphcea dilatata 
 var. Tucumcarii and the Ostrea Marshii, I consulted all the 
 books on the subject: Morton's Synopsis of the Cretaceous etc., 
 Roemer's Die Kreidebildungen von Texas, and Shumard's Pale- 
 ontology of the Red river of Louisiana. The figure in Morton's 
 Synopsis, pi. 15, fig. 9, is not good, and the text is very un- 
 satisfactory, so that I do not think it is possible to determine 
 exactly what Morton means by his G. Pitcheri, with only his 
 book in hand. Roemer gives a very good description of the 
 G. Pitcheri, p. 73 and 74, and his figures are tolerably good, 
 especially fig. 1 c; Roemer says that he has seen at Phila- 
 delphia the original specimens of Morton, but that they were 
 very imperfect and he found it difficult to identify them with 
 his own specimens; notwithstanding which, he does so and 
 says they are the same species, which he calls G. Pitcheri. In 
 Shumard's Paleontology of the Exploration of the Red river of 
 Louisiana, the descriptions of fossils are excellent, but the fig- 
 ures are miserable and cannot be of any use for comparison. 
 In saying this, I wish it to be understood that I do not intend 
 
AMERICAN GEOLOGY. 7 
 
 to blame Mr. Shumard, for it is not his fault; I wish merely 
 to state the fact that the drawings are useless. Besides the 
 study of books, I have myself seen very extensive collections of 
 Cretaceous fossils made at Fort Washita , Preston , New Braun- 
 felds , Trinity river, etc., and I have also seen the Cretaceous 
 rocks on the banks of the False Washita , and Canadian riv- 
 ers , and in the valley of the Rio del Norte near Albuquerque 
 and Galisteo; so perhaps you will admit that the following view 
 of the question was not adopted without due consideration of 
 the subject. A. The Gryphcea dilatata var. Tucumcarii differs 
 from all the fpssils found at Fort Washita. B. The Ostrea 
 Marshii is different from the Ostrea snbovata Shumard, and fur- 
 ther, it has never been found, to my knowledge, at Fort Wa- 
 shita, nor in any other cretaceous locality of Texas. 
 
 Second. I have not yet seen any fossil from Fort Washita 
 that could be identified with those of Pyramid Mount, neither 
 have I found any at Pyramid Mount identical with those of 
 Fort Washita. 
 
 Third. Roemer may have been mistaken, though I think 
 not, in identifying the G. Pitcheri of Morton with that which 
 he found at New Braunfelds , also called by him G. Pitcheri , 
 but, however this may be, I am convinced that the G. Pitcheri 
 of Morton is not the Gryphcea dilatata var. Tucumcarii , and then 
 it will be a third species different from the two others. 
 
 Fourth. The description of Shumard (see: Paleontology, 
 Appendix E, p. 205, in Explorations of the Red river of Loui- 
 siana) is exactly that of my G. Pitcheri and entirely different 
 from the description of the G. dilatata var. Tucumcarii. I saw 
 the collection of Dr. Geo. Shumard at Fort Smith in June and July 
 1853 and then he had not a single specimen of the Gryphcea 
 dilatata var. Tucumcarii. 
 
 Fifth. I am certain from my own observations , that the 
 G. Pitcheri of Morton does not range through the whole series 
 of the Cretaceous formations of Texas and New Mexico , 
 and Dr. Shumard must have confounded together three or four 
 different species of Gryphcea under the single name of G. Pit- 
 
8 AMERICAN GEOLOGY. 
 
 cheri, in order to arrive at such a conclusion. If true, this 
 would be unique in the Cretaceous rocks , where a fossil never 
 has been found to range from the base to the summit of the 
 formation in the same country. 
 
 Sixth. Morton says in his Synopsis that the original spe- 
 cimens of his G. Pitcheri were picked up on the plains of the 
 Kiamesha, and at the falls of Verdegris river, by Dr. Pitcher; 
 so far as I know , no other Geologist has ever visited these 
 two localities, and I think a fair way of settling for ever the 
 question of the identity of the Pyramid Mount fossils with spe- 
 cies found at Fort Washita, the plains of the Kiamesha, and Ver- 
 degris river, would be for a Geologist to visit these different 
 localities and collect carefully all the fossils he, can find. My 
 original specimens figured in the Bulletin de la Soc. Geol. de 
 France and in my Geology of North America, are deposited in 
 the Museum of the Geological Society of London and can be 
 always easily consulted. For my part, I hope such a Geo- 
 logist will be found before long, and I am too much a friend 
 to the truth not to submit at once to the result of such a 
 comparison. 
 
 Seventh. It is almost needless to say that I consider 
 the Jurassic rocks of Pyramid Mount as of the same age with 
 those of the Black Hills, and not far beneath them as you 
 think. 
 
 Eighth. In your letter of the 22th August 1858 you say: 
 You were certainly mistaken in supposing we had identified 
 the Trias in Nebraska ; we are not however disposed to take 
 offence at the form of your note in the Bibliotheque Uni- 
 verselle, as our remarks in the Intelligencer were too brief to 
 be fully understood by you. Dr. JIayden merely sent them 
 to you because he thought it would be gratifying to you to 
 know we had found reliable paleontological evidence of the 
 existence of Jurassic and Permian rocks in Nebraska and 
 Kansas. Perhaps I am mistaken; but I think in the incom- 
 plete section given by Hayden in the second edition of his 
 memoir entitled: Explanations of a second edition of a Gcolo- 
 
AMERICAN GEOLOGY. 9 
 
 gical Map of Nebraska and Kansas, I see evidence of the 
 existence of a portion of the Trias in his Permian. The Red 
 Buttes on the road between Fort Laramie and Rock Indepen- 
 dence are certainly not Jurassic, though colored as such on 
 Hayden's map, but of the Triassic age as I said in my first 
 Geological Map of 1853. I do not doubt that the Trias exists 
 on both sides of the great Missouri valley, at the Black Hills, 
 and on the border of the Plateau du Coteau des Prairies, con- 
 tinuing by the head waters of Red river to Lake Superior. 
 As for the reliable paleontological evidence of the existence of the 
 Jurassic in Nebraska, I do not think it in any degree more re- 
 liable than mine for New Mexico, and when you urged so earn- 
 estly in 1856 and 57 that there were no such formations as 
 Jurassic and New Red in Nebraska, I maintained with no less 
 certainty that they existed there, notwithstanding your repeated 
 denials. Besides it will be just as easy for the learned Pale- 
 ontologist James Hall to prove that your Jurassic fossils from 
 the Black Hills are identical with Cretaceous fossils of Fort 
 Washita , as it has been for him to prove the supposed iden- 
 tity of my Jurassic fossils from Pyramid Mount with Fort Wa- 
 shita Cretaceous forms. 
 
 Ninth. I have not indicated the Permian between Fort 
 Smith and Albuquerque, as I found unquestionable evidence 
 of its existence only near the Rio Colorado Chiquito; but I 
 have always strongly suspected that the New Red Sandstone 
 between Delaware Mount and Beavertown was of Permian age. 
 Having found no fossils, and being the first geologist to enter 
 those regions, I was not able when in the field to declare 
 exactly the age of those strata. All that I knew fhen was, that 
 after having left the Carboniferous limestone of Delaware 
 Mount, I entered upon strata belonging to another and younger 
 formation; and it was only after having passed Beavertown 
 that I saw clearly I was upon the New Red Sandstone. Since 
 the discovery of Permian in Kansas I am still more inclined 
 to the belief that the strata between Delaware Mount and Beaver- 
 town are Permian. Thus you see I include the Permian in 
 
10 AMERICAN GEOLOGY. 
 
 the New Red Sandstone formation. I know that good reasons, 
 based exclusively on paleotological grounds, have been ad- 
 vanced by geologists desirous to place the Permian in the Pa- 
 leozoic; but I think the old classification a better one, and 
 more, I think the term Permian, at least as given by Mur- 
 chison for the strata of the government of Perm (see: The Geology 
 of Russia in Europe and the Ural mountains , vol. I, p. 137 etc.), 
 a very improper one. There are strong suspicions that Mur- 
 chison has put in his Permian of Russia , a part if not the whole 
 of the Trias-, and I am almost certain that, if geologists accept 
 the Russian Permian as Murchison has defined it as the type , 
 the Trias will disappear from classification in Asia, Africa, 
 America, and Australia. 
 
 Tenth. Allow me respectfully to suggest to you that I 
 cannot see anything of cretaceous in what you call N 1 of 
 your Nebraska section. It appears to me that you put in your 
 N 1, or Lower Cretaceous, all sorts of strata of different ages, 
 except true cretaceous rocks. 
 
 I can assure you that the strata on my route near the 
 35th parallel of latitude, which, in your memoir entitled: Re- 
 marks on the Tertiary and Cretaceous formations of Nebraska , and 
 the parallelism of the latter with those of other portions of the 
 United States and Territories, p. 17 and 18, you consider as 
 equivalent to your N 1 and N 2 of your Nebraska section, 
 are not Cretaceous, but Keuper and Jurassic. Not having visited 
 Kansas or Nebraska, I have no decided opinion with regard 
 to the Geology of those countries , for I profess the doctrine 
 that geologists must see with their own eyes in order to de- 
 cide the difficult questions of the science; and all that I have 
 said about it is approximative and based upon my knowledge 
 of the geology near the 35th parallel. With this reservation 
 I will submit to you the following remarks upon your Lower 
 Cretaceous NO 1. You admit in one of your letters that the 
 rocks near the mouth of the Judith river on the Upper Mis- 
 souri are not the type of your formation N 1 , and you say 
 it is highly probable Jurassic rocks will be found there, so I 
 
AMERICAN GEOLOGY. H 
 
 will say nothing as to the Judith river strata ; another survey , 
 more careful than the first reconnaissance of Dr. Hayden , is 
 evidently required in order to arrive at the true geological 
 structure of the vicinity of Fort Benton. The strata which con- 
 stitute the type of your Cretaceous N 1 , are brown sandstones 
 and various colored clays seen along the Missouri near the 
 mouth of Big Sioux river. You saw there those strata hold- 
 ing a position immediately beneath N 2 of your Cretaceous 
 section; and in them Dr. Hayden made a large collection of 
 leaves , unquestionably dicotyledonous and having quite a mo- 
 dern aspect. Rough sketches of some of these leaves were 
 sent by you to my friend Prof. Heer , who has examined them 
 carefully with the following result. Liriodendron Meekii n. sp. 
 Heer; species very analogous to the L. Procaccini linger. The 
 latter is a very characteristic fossil of the Miocene of Switzer- 
 land and Italy. Populus leuce Rossmassler? The identity of 
 your leaf with this species is not certain, owing to the imper- 
 fections of the drawing, but at all events yours is very closely 
 allied to the P. leuce, a characteristic fossil of the Ligurian of 
 Bagnasco, Piedmont, or the Lower Miocene of Lyell, or the Oli- 
 gocene of Germany. Populus cyclophylla n. sp. Heer. Laurus 
 />n'wiV/emaUnger? Your leaf is very probably identical with this 
 species , which is a very characteristic fossil of the Lower Mio- 
 cene of the Isle of Wight. Sapotacites Haydenii n. sp. Heer. 
 The genus Sapotacites is Tertiary. Phyllites n. sp. The genus 
 is special to the Lower Miocene of Bohemia. Leguminosites 
 Marcouanus n. sp. Heer. This genus is allied with the genus 
 Ccesalpina still living now. In conclusion Prof. Oswald Heer 
 says that he sees nothing of the Cretaceous age in these leaves, 
 and he thinks the flora indicates the Lower Miocene. If this 
 conclusion is correct, the beds containing them near the mouth 
 of Big Sioux river, are of the same age as the Miocene of 
 White river or Mauvaises Terres and must belong to a sort 
 of outlier of the great Tertiary basin of Nebraska. Of course 
 in such a case these strata cannot hold a position beneath your 
 Cretaceous rocks NO 2, but that question must be elucidated 
 with the greatest care in the locality itself. 
 
12 AMERICAN GEOLOGY. 
 
 I am much inclined to adopt the opinion of Prof. Heer, and 1 
 suspect that your Lower Cretaceous N 1 of the mouth of Judith river 
 is partly Jurassic and partly Miocene-, the Baculites found with the 
 leaves being probably a cretaceous Baculites of the neighboring 
 strata that has been washed away from the cliff during the deposi- 
 tion of the Tertiary rocks. To continue, I also regard your 
 Black Hill Lower Cretaceous N 1 with dicotyledonous leaves 
 as Miocene as well as the similar formation indicated some- 
 where in Kansas by Major Hawn. Further, after a careful exa- 
 mination, Prof. Heer thinks that the deposit in the vicinity of 
 Fort Bent, from which Lieut. Abert obtained leaves, is also 
 Lower Miocene and equivalent to your formation of the Big Sioux 
 river; and that the Muddy river coal discovered by Col. Fre- 
 mont is of Tertiary age instead of Jurassic as it was pronounced 
 by James Hall. The fossil leaves figured by Prof. Bailey in 
 Abert's Report (see: Report of Lieut. J. W. Abert, of his exa- 
 mination of New Mexico, in the year 1846 47) belong to two 
 species, the lanceolate leaf is identical with your Laurus pri- 
 migenia of the Big Sioux , and the large cordate leaf is a spe- 
 cies of Ficus ; a Tertiary genus still living. But I will remark 
 that Abert says p. 523 of his Report, that he did not find 
 those leaves himself at the Raton mountain; he examined the 
 coal, but was unable to find a single impression of leaves, 
 and the specimens figured were given to him at Fort Bent by 
 hunters, so the exact place of the leaves is doubtful; they may 
 come from other strata of the vicinity of Fort Bent. I say this 
 because I suspect the bituminous coal from the Raton to be 
 the equivalent of the coal I found at Ojo Pescado near Zuni 
 which is of Jurassic age. James Hall says: Glossopteris Phil- 
 lipsii? Brong. I have referred this species to the G. Phillipsii, 
 as being the only description and figure accessible to me, to 
 which this fossil bears any near resemblance. The geologi- 
 cal position of that fossil is so well ascertained to be the 
 schists of the upper part of the oolitic period , that , relying 
 upon the evidence offered by a single species, we might re- 
 ft gard it as a strong argument for referring all the other spe- 
 
AMERICAN GEOLOGY. 13 
 
 cccimens to the same geological period.)) (See: Colonel J. C. 
 Fremont's Exploring Expedition to the Rocky Mountains, and to 
 Oregon and North California , in the years 1842 43 44, p. 305; 
 Washington , 1845.) Now Prof. Heer thinks the supposed Glos- 
 sopteris Phillipsii is nothing else than your Laurus primigenia of 
 Big Sioux river; that the leaf, pi. II, fig. 4, is probably a Quercus; 
 and as for the Ferns , no one of Hall's figures is characteristic 
 of the Jurassic period or any other special formation, as the 
 Ferns range from the Devonian until now , and when new are 
 no evidence as to the age of a deposit. 
 
 The coal that I found at Ojo Pescado near Zuni is Ju- 
 rassic , from its stratigraphical position above and beneath rocks 
 that I consider to be undoubtedly of that age. When there 
 I looked sharply for impressions of leaves , but I found none, 
 and I am not aware that any have been found since in that 
 region of Zuni, Fort Defiance and Canon de Chaca. 
 
 I was unable to find a single impression of leaves during the 
 whole of my exploration in the Triassic of the Prairies, so they 
 must be scarce. Only in that part of the Trias that I look upon 
 as equivalent to the Bunter Sandstein I found a Pinites allied 
 to the Pinites Fleurotii of Europe, numerous specimens of 
 Araucarites called by Gceppert Araucarites Mb'llhausianus (see: 
 Tagebuch einer Reise vom Mississippi nach den Kusten der Sudsee; 
 von B. Mb'llhausen; p. 492; Leipzig, 1858), and several shells 
 of the genus Cardinia. In America, as in Europe, the Trias 
 is generally very poor in fossil remains , and I think they will 
 never be found in great abundance in the Far West. 
 
 Let me call your attention to the following remark. Is it not 
 strange that Prof. Heer and Dr. Leidy have arrived at the same 
 conclusion in regard to the age of the lower part of the Tertiary 
 formation of Nebraska, both of them calling it Lower Miocene, 
 basing their opinion , the one upon Plants and the other upon 
 Mammalia and Chelonians, and Heer having no knowledge what- 
 ever of Leidy's publications! 
 
 Finally, I maintain all the observations contained in my 
 preliminary report to Capt. Whipple as exact, notwithstanding 
 
14 AMERICAN GEOLOGY. 
 
 all the objections advanced against them. From your expe- 
 rience of the Indian Country , you will probably agree with me, 
 that it is much easier to make objections from a comfortable 
 room in a large town, than to observe in the wilderness of 
 the Rocky Mountains \ and you will permit me to suggest, that 
 it would be better for the Science if my adversaries would 
 go themselves on the field and follow my route near the 35th pa- 
 rallel, instead of making a show of their powers of argument 
 in Sillimaris Journal, or at the meetings of scientific associa- 
 tions. I have done, and I will say no more until my next 
 exploration of the Rocky Mountains ; for I hope soon to return 
 to my home in Boston , and from there I will try again to re- 
 ach some part of those beautiful mountains which you and I 
 were the first to explore geologically. As an illustration of 
 the difficulties I had to encounter when with Capt. Whipple's 
 expedition, I will extract from my private note-book the fol- 
 lowing remarks. 22th December 1853. For the last ten 
 days the cold has been very severe , the thermometer being 
 at 7 Fahrenheit with frequent snow storms. We started at 
 ten in the morning leaving the Rio Colorado Chiquito near the 
 cascade, and directing our course due West, to the South of 
 the San Francisco volcano. From Zuni to the cascade of the 
 Rio Colorado Chiquito, our road passed over all the strata 
 of the Triassic rocks , and our starting point of the 22d was 
 on red sandstone, that I consider as the equivalent of the 
 Bunter Sandstein. After having marched three miles, the red 
 sandstone gave out, and was replaced by strata of Magne- 
 sian Limestone cropping out from beneath the Bunter Sand- 
 stein. Just at that moment a very severe snow storm came 
 on , and I was obliged to turn my back to the wind and try , 
 by scratching away the snow with my hammer, to collect some 
 ((specimens and make a few observations on this new for- 
 mation. The snow storm continued steadily until six o'clock 
 in the evening, when we encamped on volcanic lava. 
 Thus in addition to the fear of Indians, for we were then in 
 the middle of the Navajos country, which obliged us to keep 
 
AMERICAN GEOLOGY. 15 
 
 together and not to be more than half a mile in the rear of 
 the party, I had to battle with a violent snow storm, and I 
 think every one will admit the difficulty of making geological 
 observations under such circumstances. Nevertheless I saw 
 perfectly well that the stratigraphical position of those Dolomitic 
 beds was beneath the Bunter Sandstein, in accordance of stra- 
 tification with it; and the lithological character as well as the 
 position showed me that it was the Magnesian Limestone, or Per- 
 mian formation. Further, I found some very imperfect spe- 
 cimens of fossils differing in form from Carboniferous fossils, 
 and I have no doubt that fossils are common in these strata 
 from the fact that I found some under such disadvantageous 
 circumstances. If the collections I made with Capt. Whipple 
 had not been taken from me, perhaps I might have been able 
 to determine some of them by carefully separating them from the 
 enclosing rock. At all events, on Stratigraphical and Litholo- 
 gical grounds, I maintain that the Magnesian Limestone of the 
 Canon Diablo and on our road on the left side of that Canon , 
 are of Permian age. 
 
 We are far from agreeing, as you see, on many capital 
 questions relating to the Geology of the Far West ; but I join 
 you heartily in the conclusion of your letter, when you say: 
 In conclusion I would state that we can differ in opinion 
 without entertaining hard feelings. We certainly desire to 
 arrive at truth, even if it should not accord with our pub- 
 dished opinions.)) 
 
 Very truly Yours 
 
 JULES MARCOU. 
 
16 AMERICAN GEOLOGY. 
 
 P. S. In Dr. Hayden's paper, entitled: Explanations 
 of a Second Edition of a Geological Map of Nebraska and Kansas, 
 p. 8, he says: In our remarks of the 2d of March, upon 
 the discovery of supposed Permian rocks in the West, both 
 Mr. Meek and myself wish to be understood as referring to 
 their existence in Kansas and Nebraska. Our object being 
 simply to announce our conclusions derived from the study 
 of fossils collected from these rocks in the West, we did 
 not refer to their supposed prior discovery in Pennsylvania and 
 on the Atlantic coast, nor were we able to judge of the evi- 
 dence of their existence in those localities, it being based, 
 for the most part, upon the remains of Vertebrata, which 
 are out of our line of investigation.* It appears to me to be 
 very unphilosophical to ignore the discovery of Permian rocks 
 by Professor Emmons in North Carolina, because it is based 
 on remains of Vertebrata and the Vertebrata are out of your 
 line of investigation. What will you say if Geologists refuse 
 to consider your observations on the Tertiary Basin of White 
 and Niobrara rivers, because your evidence is based entirely 
 On Vertebrata and Chelonians. Geology will never progress 
 if each one of us reject the observations of others because 
 they are out of his line of investigation. 
 
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