268 



NA TORE 



[July 23, 1891 



the sylvicultural notes are Quercus pedunculata and 

 Quercus sessiliflora. Botanists are well aware that the 

 maintenance of distinctive characters between these 

 two and others of the European species of Quercus 

 is difficult ; so much so, that the best authorities on 

 English trees have decided to re-establish the old 

 species of Linnaeus, Quercus Robur, and to regard the 

 two species named merely as forms or varieties. The 

 forester has a different task, and for him the mode of 

 growth and the requirements of these two oaks are so 

 different that he must keep them separate. It will suffice 

 to mention one point, which has not perhaps been brought 

 out sufficiently by the author. The mixed woods 

 in which Quercus sessiliflora is associated with the 

 beech, the hornbeam, and the silver fir have been 

 mentioned above. In natural high forests this species is 

 only found in company with other trees, and particularly 

 with the three kinds named. The pure or nearly pure 

 coppice woods of Quercus sessiliflora in France and 

 Western Germany are an exception ; these, however, 

 have been converted into pure woods by the long- 

 continued cutting out of beech, hornbeam, and soft 

 woods. Quercus pedunculata, on the other hand, does 

 form pure high timber forests of considerable extent. 

 Such are found both in Northern and Southern Europe, 

 not on hilly ground, but always on deep alluvial soil. 

 Instances are the forests on low ground along the Elbe 

 and other rivers of North Germany, the magnificent pure 

 forests of that tree on the banks of the Adour river near 

 Dax in Gascony, and similar ones in the peninsula of 

 Istria, south of Trieste. There is underwood on the 

 ground in the forests named, but it merely consists of 

 thorns and low shrubs. The two species, Quercus sessili- 

 flora and pedunculata have dififerent requirements and 

 require somewhat different treatment. This, however, is 

 a small matter. These sylvicultural notes are most 

 valuable, and it is satisfactory that the Weymouth 

 pine and the Douglas fir have been included among 

 them. 



The second volume of Dr. Schlich's manual, like the 

 first, will be an immense help to the students who are 

 trained at the Coopers Hill College for forest service in 

 India. It will be a great boon to all who are charged 

 with the management of forests in India, in the colonies, 

 and in the United States of North America. And it may 

 perhaps be hoped that in Great Britain also this excellent 

 "book will in course of time tend to awaken a more general 

 interest in the good management of its woodlands, which 

 are very extensive, and which some day may be of 

 considerable importance and of great value to their 

 proprietors. D. Brandis. 



THE APPLICATIONS OF MODERN 

 CHEMISTRY. 

 Dictionary of Applied Chemistry, Vol. II. (Eau-Nux). 

 (London: Longmans, 1891,) 



THE editor of a dictionary of applied science, such as 

 the volume before me, has in these days no enviable 

 task to perform : much is required of him, and the diffi- 

 culties with which he has to contend are great. Prof. 

 NO. 1 134, VOL. 44] 



Thorpe has acquitted himself well, for though there may 

 be, indeed there are, many points with which the expert 

 can find fault, yet these are generally matters of detail, 

 and on the whole the work has been satisfactorily done, 

 so that the second volume will be found to be quite up to 

 the high level of the first. The industries which owe 

 their foundation to the science of chemistry now progress 

 with such giant strides, that processes which last year 

 were the newest and best may this year be so improved 

 as to be rendered obsolete, so that an article printed 

 at the commencement of a volume may become an- 

 tiquated before the last article is in type, whilst data 

 unattainable when the article was written are super- 

 seded by some more recently published. As an example 

 of this, I may take that upon " gas coal," written 

 by a most competent authority, Mr. Lewis Wright. 

 On p. 177 will be found a table giving the weight of coal 

 carbonized by all the authorized gas undertakings in the 

 kingdom, exclusive of those of local authorities, for the 

 year ending March 25, 1886. Since these tables were 

 printed, a Board of Trade return for 1890 has been pub- 

 lished. In 1886, 8,378,904 tons of coal were carbonized ; 

 in 1890 the figure rose to 9,663,011. In 1886 the mileage 

 of mains was 18,967 ; in 1890 it had increased to 21,584. 

 These numbers point out the enormous extent of the 

 coal-gas industry in this country, and show clearly that it 

 is not suffering from the competition of electric lighting ; 

 indeed, this competition is favourable to the sale of gas, 

 for we see that our streets are now better lighted than 

 formerly, and the consumption of gas in many shops is 

 increased, in order to vie with the splendour of their 

 neighbours' electric light. 



As a critic is bound to criticize, I may point out some 

 few faults of commission and omission which have 

 struck me in reading through this generally excellent 

 article. 



The important steps which have recently been taken 

 in many large works for charging and drawing the gas 

 retorts by mechanical means are barely referred to. 

 Great economy is doubtless effected where such labour- 

 saving mechanical appliances have been adopted, and a 

 description of these would have been of interest, as the 

 labour agitation in our gas-works has brought engineers 

 face to face with this question. Another point upon 

 which a statement would have been of value is the most 

 improved arrangements of the purifying house, and the 

 methods adopted for charging and discharging the puri- 

 fiers. That ' ' the whole of the sulphuretted hydrogen, car- 

 bonic acid, and carbon disulphide can be easily and 

 economically removed" (p. 200) by a combined system 

 of oxide and lime, and with a proper arrangement of 

 purifiers, is a statement to which many gas engineers 

 will demur. The London companies, especially, who 

 have a legal standard limit for sulphur compounds, find it 

 both difficult and expensive to keep down the impurities 

 to the necessary point. The illustrations given in this 

 article are scarcely worthy of the letter-press. Figs. 22 

 and 23 do not give an idea of the construction of a 

 modern gas-holder, some of which now have the enormous 

 capacity of ten million cubic feet, and are marvels of en- 

 gineering skill. A description of the latest improvements 

 would have added interest to the article. 



