SCIENTIFIC NEWS. 



[Mar. 23, 18 



SOUTH LONDON ENTOMOLOGICAL AND 

 NATURAL HISTORY SOCIETY. 

 On March 8, Mr. Carrington read a paper on the British 

 Salmonidae, with particular reference to the salmon, the 

 trout, the char, and the grayling. Many interesting facts 

 were mentioned concerning the remarkable changes pro- 

 duced in these fishes by removal to a diiferent climate, or 

 even by transfer to a river of a different character. 

 Hybridisation is very successful among different species 

 of this genus, and one of the forms thus produced pro- 

 mises to be of practical importance. The fish in question 

 reach the weight .of 13-14 lbs. and have the great 

 advantage over the salmon that it remain s all the j'ear 

 round in lakes or streams without needing or seeking to 

 return to the sea. An interesting species of the 

 Salmonidae is the " pullen " or "fresh-water herring " of 

 Lough Reagh, which is rarely met with in the London 

 market. 



GLASGOW NATURAL HISTORY SOCIETY. 

 At the meeting held on the 28th ult.. Dr. Marcus Calder 

 exhibited living specimens of the black rat {Mns ratliis), 

 a species which was formerly abundant in this country, 

 but has become almost extinct within recent years, 

 although single individuals are sometimes obtained in 

 the vicinity of seaports. It is believed to have been 

 extirpated by the common brown rat {Mus deciimamis), a 

 larger and more powerful species, which has rapidly 

 spread over the country. Dr. Calder stated that the 

 specimens had been captured at Greenock, where the 

 black rat has been re-introduced, probably through the 

 agency of shipping, and is at present rather abundant in 

 one part of the town. Mr. A. Somerville, exhibited a 

 specimen of Trophon truncatidus var. scalaris, a gastropod 

 shell dredged by him in 40 fathoms off the Soay Isles, 

 lona. In the course of some remarks, he stated that the 

 type is commonly met with throughout the West of 

 Scotland, and more sparingly further south, but the 

 variety has hitherto been regarded as a Norwegian or 

 Arctic form, not occurring further south than the Shetland 

 Isles. Mr. A. Somerville, B.Sc, F.L.S., read a paper on 

 a day's dredging in 30 and 44 fathoms mud, off Portin- 

 cross, Ayrshire, and submitted a list of the shells 

 obtained, which included several rare and interesting 

 species. 



QUEEN'S COLLEGE, BIRMINGHAM. 

 Professor Tilden, in a lecture delivered recently, said : 

 Imagineaglobe about 6ft.indiam. coated withalayerof liquid 

 1-20 to 5oin. thick, and with a layer of gas ^in. thick, we 

 should then have a model which would roughly represent 

 the earth with its oceans of water and air. And just as the 

 waters of the sea consist not of pure water, but of water 

 mixed with various and varying quantities of solids and 

 gases dissolved out of the earth and air, so the atmosphere 

 consists of a mixture of two principal gases mixed with 

 small quantities of other substances, solid, liquid, and 

 gaseous, derived from the earth. The two chief com- 

 ponents of the air are oxygen and nitrogen, in the ratio 

 of about one-fifth oxygen to four-fifths nitrogen. The 

 former was distinguished by the old chemists from 

 Priestley's time as •' vital air," a sufficiently expressive 

 name when we remember that it is indispensable to 

 life. Beside the normal constituents given we have other 

 ingredients always present throughout every region of 

 the atmosphere, even in the mountains and in the open 



country, far away from man and his works, and these 

 also contribute in various ways, not wholly understood, 

 to the general effects of the atmosphere. Of course local 

 and temporary changes are produced where many people 

 are congregated together as in towns and crowded 

 buildings. Under such circumstances we get not only a 

 diminution of oxygen, but an increase of carbonic acid, 

 and especially of those indefinable organic matters the 

 presence of which is certainly very deleterious. The 

 variation to which the proportion of oxygen is liable lies 

 within very narrow limits. According to Dr. Frankland's 

 analyses, air from the top^ot Mont Blanc contains about 

 20.9 volumes of oxygen in 100 volumes of air, whilst 

 very bad air from the tunnel of the Metropolitan Railway 

 was found by Angus Smith to contain 30'6 volumes of 

 oxygen. The variation in the carbonic acid is more 

 obvious. Whilst pure country air contains about 3 to 4 

 volumes of this gas in 10,000 of air, the air of crowded 

 rooms, in mines, and in tunnels, often contains 15, 20, or 

 25 volumes of carbonic acid. A number of experiments 

 were made at the Mason College in 1883, with the object 

 of testing the effect of lighting the Town Hall with electric 

 light in place of gas. It was found that the air on 

 crowded nights contained about 20 volumes of carbonic 

 acid, and that there was no marked difference when the 

 electric light was used. But this is explained by the 

 fact that the heat of the gaseliers caused a strong 

 upward current of air through the ventilators. Now, in 

 regard to the impurities, it is only necessary to look at 

 the pall of smoke overhanging every town to understand 

 something of its effect in shutting off the light of the sun. 

 And if we want to know what is present in it, we need 

 only catch a little rainwater and evaporate it down, when 

 crystals containing ammonia, with hydrochloric acid and 

 especially sulphuric acid, can always be obtained. And 

 in connection with this matter it is not alone the 

 manufacturer whose chimney are to blame, though it 

 would be easy in this town to point to cases where, in 

 defiance of every legal and moral consideration, and dis- 

 regarding the injury to other people's health and 

 property, dense columns of black smoke are daily dis- 

 charged into our very streets. The present system of 

 burning coal in open grates — a system dear to the British 

 householder, who likes to have a fire he can poke — is 

 really the cause of the evil. That the evil is a serious 

 one is obvious when we observe that London is rapidly 

 becoming uninhabitable at times which are not now as 

 formerly confined to the dark months of November and 

 December. It has long been a favourite idea with me 

 that private chimneys ought not to be allowed. The 

 smoke together with the air from sewers should pass 

 together through underground culverts, where the soot 

 would be deposited, and the gases, then comparatively 

 harmless, should be delivered up tall shafts (which might 

 be made as ornamental as church spires and towers), 

 100 feet or more above our heads. Such a system would 

 require very little alteration in the structure of existing 

 houses, and would be easily carried out in new ones. 

 But no change of this kind is likely to be brought about 

 until the public is better instructed about such matters, 

 and until a general recognition of the evils of the existing 

 state of things leads to some united action. 



SOCIETY OF ENGINEERS. 

 At a meeting of the Society of Engineers, held at West- 

 minster Town Hall, on March 5th, Mr. A. T. Walmisley 



