I04 



NA TURE 



[May 30, 1 90 1 



any of them have been subjected to that minute dissection 

 which modern vulcanology and petrography now demand. 

 The Itahan geologists, however, have at last taken up the 

 investigation in considerable detail, and are issuing excel- 

 lent maps and monographs of dififerent volcanic districts, 

 which well deserve the careful attention of all who take 

 an interest in the progress of volcanic geology. To some 

 of the latest of these publications a brief reference may 

 here be made. 



The Italian Geological Survey has entered upon the 

 study of the volcanoes of Central Italy and their products, 

 and as a commencement has issued a detailed account of 

 that remarkable volcanic centre which forms the group of 

 the Alban Hills to the east of Rome. This work has 

 been accomplished by one of the staff, Mr. V. Sabatini, 

 who has long been known for his geological enthusiasm.' 

 It forms a volume of nearly 400 pages, with an excellent 

 map of the region, ten plates of views and petrographical 

 sections and 79 figures inserted in the text. After a brief 

 introduction devoted to a discussion of some of the 

 theoretical principles involved in the interpretation of vol- 

 canic phenomena, the author proceeds to give a sketch of 

 the topography of the region and of the position of its 

 several eruptive vents. He recognises, as at Vesuvius, 

 the records of two great periods in the volcanic history. 

 The first, one of conspicuous vigour, which built up a 

 large cone that was finally demolished by a stupendous 

 explosion; the second, one of minor force, whereby a cone 

 was formed within the original circuit. Each of these 

 phases has been attended with the production of second- 

 ary or adventitious cones, and the author endeavours to 

 trace a series of lines of fissure along which, in his opinion, 

 these cones have been produced. It is to be noted that 

 some of his lines appear to rest merely on the evidence of 

 carbonated or sulphurous springs, and even where they 

 run from cone to cone some effort of imagination is needed 

 to picture the lines of fissure as he gives them. In 

 Southern Italy the geologists are less fanciful in dealing 

 with the unseen substructure of their volcanoes. 



The second chapter treats of the various hypotheses 

 which have been proposed in explanation of the origin of 

 the Roman Campagna and the Alban Hills, and especially 

 of the tuffs so widely developed in that region. A detailed 

 description of these tuffs is given ; they are classified as 

 lithoid, homogeneous, granular, pumiceous and earthy, 

 and reference is made to the terrestrial flora and fauna 

 enclosed in them. Their plants include many familiar 

 living species. On Monte Celio, land-shells were found ; 

 on Monte \'erde, the molluscs were of fresh- water species; 

 in the tuffs between Nettuno and Astura, Meli has col- 

 lected a considerable number of marine and estuarine 

 forms, while a large assemblage of bryozoans has been 

 gathered from the volcanic tuffs of Anzio and Nettuno. 

 The succession of the different varieties of tuff is next 

 given as displayed in many sections in and around Rome, 

 and an attempt is made to estimate the cubic contents of 

 the vast sheet of tuff which has been discharged from the 

 Vulcano Laziale. 



The third chapter deals with the nature and classifica- 

 tion of the Latian lavas. These are grouped into normal 

 leucitites and leucotephrites. The alterations which they 

 have suftered are described, such as the transformation 

 of leucite into felspar. Detailed descriptions are then 

 given, in chapters iv. and v., of the rocks of each important 

 part of the outer and inner cones of the volcano, and the 

 author, following a practice for which he no doubt can 

 cite high authority, adopts a somewhat complicated and 

 cumbrous system of symbols to express the petrographical 



1 1 vulcarii dell halia Centrale e i loro Prodotti. Parte Prima— Vulcano 

 Laziale, di V. Sabatini. Roma, 1900. (R. Ufficio Geologico. Memorie Des- 

 cnttive della Carta Geologica d' Italia, vol. x.). This volume, the author 

 informs us, is based on the work of 112 days in the field and the examina- 

 tion of 400 microscopic slides of rocks. The volcanic centre here referred to 

 under the name of " \ ulcano Laziale " comprises the Monti Laziali and the 

 Monti Albani and their surroundings. 



NO. 1648, VOL. 64] 



characters of each rock. Such a system may be con- 

 venient, especially where rapid comparisons of different 

 species and varieties of rocks are desired by a student 

 who has taken the time and labour necessary to under- 

 stand it and commit it to memory. But life is too short 

 and geological literature is too long for such a task on 

 the part of ordinary readers. It would not have cost 

 much more type to have accompanied the symbols with 

 a brief statement of the composition of the rocks in plain 

 language. The origin and constitution of the craters of 

 Nemi, Castel Gandolfoand Ariccia take up the next three 

 chapters. The author here, as in the rest of the volume, 

 deals less fully with the tectonic than with the petro- 

 graphical part of his subject. He would have added 

 much to the geological interest of his memoir had he 

 given more ample details of the structure of the great 

 volcano and presented a clear and vivid outline of the 

 whole succession of volcanic phenomena of which it pre- 

 serves the record. Perhaps he may intend to deal with 

 these parts of his subject in a subsequent treatise. A 

 useful bibliography is appended to the volume. It is 

 much to be desired, however, that precise references had 

 always been given to the passages in the works of the 

 authors whose names are cited in the text. The con- 

 tinuation of the important research of which Mr. Sabatini 

 gives here the first instalment will be awaited with much 

 interest. 



In Southern Italy the investigation of volcanic phe- 

 nomena is naturally incited by the irresistible attractions 

 of the active volcanoes of that region. The study of the 

 extinct cones and craters, however, has perhaps rather 

 been retarded by the abundant opportunities offered 

 there of witnessing the actual progress of eruptions. 

 Within the last few years the subject of the older vol- 

 canoes has been taken up by several observers, who, 

 without the resources of the National Survey to assist 

 them, have nevertheless been successful in bringing much 

 fresh information to light. Two of these geologists — 

 Prof. (j. de Lorenzo, of the University of Naples, and 

 Prof. C. Riva, of the University of Pavia — deserve 

 especial commendation for the enthusiasm of their re- 

 searches. The volume just issued of the Transactions 

 of the Royal Academy of Naples contains two detailed 

 memoirs, one by Prof. G. de Lorenzo on the well-known 

 Monte Vulture between Naples and the Adriatic, the 

 other by the two authors conjointly on the seldom-visited 

 crater-island of Vivara between the islands of Ischia and 

 Procida in the Bay of Naples.' 



The memoir on Monte Vulture extends to 207 

 closely printed quarto pages, and is illustrated by numer- 

 ous figures in the text as well as a map and a number of 

 excellent plates in photogravure, of which one is here 

 reproduced. In an introduction, the history of obser- 

 vation regarding this ancient volcano is briefly sketched. 

 The author then proceeds to describe the various sedi- 

 mentary series through which the volcanic explosions 

 took place. These consist of Trias, Cretaceous, Eocene 

 and Miocene formations, together with Pliocene and 

 Pleistocene deposits both marine and terrestrial. The 

 stratigraphical relations of these various groups of strata 

 had already been discussed by M. de Lorenzo in a paper 

 on the geology of the Southern Apennines, published in 

 1896, and they are well displayed in a plate of sections 

 accompanying the present monograph. The incomplete 

 series of Mesozoic formations is shown to have been con- 

 siderably disturbed before Tertiary time, while the Eocene 

 and Miocene deposits had likewise been plicated and 

 denuded before the Pliocene strata were laid down upon 

 them. In the southern outskirts of the mountain the 

 volcanic pile rests on the younger Tertiary groups, while 

 towards the north it spreads over the area of the Eocene 

 and Miocene "Flysch." The faulted nature of the 



