Augjisi 19, 18S0] 



NATURE 



559 



very good ; one only wishes that he had treated this part 

 of his subject more fully. 



The chapter on "Mixing and Nature of Colours "is 

 not as complete as it should be, from the almost entire 

 absence of chemical illustrations, which on such a subject 

 are invaluable. One remark, however, which often occurs 

 in this book is most admirable. "The painter should 

 always make an effort to use as few colours as possible, 

 and they should be of the most permanent kind." 



On damage to oil-paintings by gas and damp, it is 

 stated that painter's canvas is usually prepared by first 

 covering one side of it with a coat of whiting, to which 

 glue size has been added. This is hardly a correct state- 

 ment of the method employed by the best firms. The 

 canvas is treated with size rubbed in with long knives, in 

 the jelly form, it is then scraped off as bare as possible. 

 This is done to protect the canvas from the disintegrating 

 effects of the oil used in the preparation of the siu-face, 

 for oil oxidises and speedily rots canvas, and therefore a 

 coat of oil paint would not be, as stated, a protection to 

 the back of prepared canvas : better use paraffin, which 

 does not oxidise. Space will not allow a further notice of 

 the concluding chapters of this work. One or two points, 

 however, seem to require remark. " If darkening of a 

 picture is due to some chemical action in the colours 

 themselves, which is not unfrequently the case, the ori- 

 ginal condition of the work cannot be restored." If the 

 darkening be due to the action of sulphuretted hydrogen 

 or white lead, the whiteness can be restored by washing 

 with peroxide of hydrogen. 



In the directions given for painting the walls of the 

 painting-room it is advised to use prussian blue, and the 

 vehicle to be employed is spoken of as distemper colour. 

 Prussian blue is immediately decomposed by lime or 

 chalk, and therefore cannot be used with these materials. 



On the whole, one feels great pleasure in recommending 

 this book as useful to art students. As has been before 

 stated, it is matter for regret that parts of it have not been 

 more fully treated, and at the same time it must be ob- 

 served that, as regards scientific questions involved in 

 the composition of pigments and on their action on one 

 another, as well as the adulterations with which they are 

 contaminated, the subject is almost wholly untouched, 

 and we must look for some further treatise to illustrate 

 and explain these points, either from Mr. I\Iuckley orfrom 

 some other author. 



A VISIT TO ETNA 

 Un Viaggio all' Etna. Del Prof. Orazio Silvestri, di 



Firenze, Presidente del Clnb Alpino Italiano a Catania. 



(Torino : Ermanno Loescher, 1879.) 

 '"I^'HE Itahan Alpine Club has branches in all the prin- 

 -L cipal cities of the kingdom, and a good deal of 

 useful work is done every year by its members. The 

 work before us is designed not only for the benefit of the 

 Club, but to foment and foster a greater taste among 

 Itahans for exploration, by setting .before them a history 

 of their most famous mountain, and detailing the very 

 varied incidents to be met with in a journey to its summit. 

 The book is divided into eight chapters, and is furnished 

 with an appendix, which contains a list of the principal 

 monticules on the slopes of Etna, with their altitude and 



position ; the altitude of the principal towns on and around 

 the mountain ; and (to prevent imposition) the tariff 

 established by the Catanian branch of the Alpine Club 

 for the ascent of the mountain, and for visiting points of 

 interest on its flanks. 



The population of the mountain is rapidly increasing. 

 In 1871 it amounted to 314,092, divided between thirty- 

 nine cities, towns, and villages. The largest of these — 

 Catania— contains 84,397 inhabitants ; the smallest — S. 

 Agata di Battiati— 507. 



The first chapter of the " Viaggio " carries the traveller 

 from Turin to Naples, from Naples to Messina, and from 

 Messina to Catania. The passing glimpses of Vesuvius 

 and Stromboli are described, and the beautiful coast 

 scenery between Messina and Catania, which embraces 

 the Capo di Taormina, one of the most picturesque spots 

 in Europe. The second chapter describes the ascent as 

 far as Nicolosi, the last village on the route to the summit. 

 In its immediate neighbourhood are the Monti Rossi, 

 formed during the eruption of 1669, which is described at 

 some length. 



Starting from Nicolosi (Chapter III.), the traveller 

 passes over the lava of 1537, and presently enters the 

 Regiotie Selvosa; he notes the numerous groups of mon- 

 ticules scattered in various directions, rests at the Casa 

 del Bosco, 235 metres higher than Vesuvius ; and later 

 on continues his journey through a region in which the 

 vegetation becomes more and more sparse until he arrives 

 at the Casa Inglese, near the foot of the great cone. Here 

 the author bursts out into an " Inno alia Natura " impro- 

 vised by the poet Mario Rapisardi on the occasion of his 

 visit to the summit, and of which the following is a 

 specimen : — 



" SoiTidi a uoi, sorridi, 



O Dea ! sia che de I'Etna 

 T'amiamo oggi invocar, 

 O dai pietrosi lidi, 



Ove fuggente e pavido 



Scagliossi il poveretto Aci uel mar." 



About two o'clock in the morning the traveller leaves 

 the Casa Inglese for the summit (Chapter IV.). The 

 severe climb up the cone of cinders (angle froni 32° to 

 35°) is attended by some difficulty of respiration, both 

 from the rarity of the atmosphere, and the presence of 

 volcanic exhalations. The phenomena preceding sunrise 

 are described, the gradual illumination of the scene, and 

 the projection of the shadow of the mountain over Sicily. 

 An account of the appearance of the great crater con- 

 cludes this chapter. A description of the eastern flank 

 of Etna and the Val del Bove furnishes the matter for 

 the two succeeding chapters. The geology of the moun- 

 tain is herein discussed ; specially the theory of two 

 axes of eruption, warmly supported by LyeU and other 

 geologists. 



After resting a night at Giarre, the traveller visits the 

 eruptive craters of 1865, passing by the villages of S. 

 Giovani and S. Alfio, and through the ivood of Carpi- 

 netto, which contains the celebrated Cas/agno del Cento 

 Cavalli. A detailed account of the eruption of 1865 

 which was minutely studied by Prof. Silvestri, is given in 

 this part of the book (Chapter VII.). The last chapter 

 is a very comprehensive one. It takes the reader com- 

 pletely round the northern, western, and southern flanks 



