June. 1912. 



KX(^\VLEDGr-:. 



2ii 



Bole usually short ; all the main branches of young trees 

 ascending at a very acute angle ; crown very large ; laminae 

 acute-acuminate, of the terminal leaves about five inches long ; 

 petioles about a half inch long, usually hairy. — ''HUXTINGTON 

 Elm ((7. glabra X nitcns — \h) X U. vegeta.) 

 V. 



Tree tall at maturity ; bole long, straight ; lower branches 

 wide-spreading ; crown rather large : samara small, rather 

 less than half inch broad, obovate ; laminae acute or 

 acuminate, very smooth and shiny above, of the terminal 

 leaves about three and a half to four and a half inches long 

 and about two inclies broad ; petiole about a half inch long, 

 glabrous at maturity. — SMOOTH-l.ii.WED Elm (U. nitens 

 Moench). 



Tree small ; laminae of the terminal leaves short, less than 

 two and three-quarters inches long. — \'I. 



VI. 



Tree not pyramidal ; lower branches wide-spreading ; crown 

 usually small, sometimes rather large when the upper 

 branches of old trees are very tortuous ; winter buds usually 

 smaller than in any other Elm ; this and U. stricta are the 

 last Elms to come into flower ; samara small, narrower than 

 in any other British Elm, being only about three-tenths of an 

 inch wide, oblong-elliptical ; laminae acute or sub-obtuse, 

 never acuminate, of the terminal leaves about two to two and 

 three-quarters inches long or even shorter, and about one 

 and a quarter to one and a half inches broad ; petiole about 

 two-fifths of an inch long, usually rather hairy and rough. — 

 Small-leaved Elm (U.sativa Miller.) 



Tree pyramidal ; branches fastigiate or sub-fastigiate. — VII. 

 VH. 



Branches fastigiate ; samarae about a half inch wide, 

 slightly obovate ; laminae about as broad as in V . sativa, 

 each half bent inwards or upwards on the midrib (when fresh), 

 subcoriaceous ; petiole as in U sativa. — t CORNISH ELM 

 (U. stricta Lindley). 



Branches subfastigiate ; laminae flat, broader (about one 

 five-eighths to one and three-quarters of an inch broad) 

 than in U. stricta. — '■ Jersey Elm (U. striata var. 

 sarniensis Moss). 



CHEMISTRY. 



By C. .AiNswoRTH Mitchell, B..\. (Oxon.), F.I.C. 



SPONT.ANEOUS COMBUSTION OF CHARCOAL.— 

 The Report of the National Physical Laboratory for 1911, 

 which has recently been published, contains (on p. 86) an 

 interesting account of the results of experiments made to 

 ascertain the liability of charcoal to undergo spontaneous 

 combustion. 



In these experiments one cubic foot of the charcoal was 

 exposed in an electrically-heated oven to temperatures which 

 were kept constant within 1" C. by means of thermo-couples. 

 An air-space of about three inches was provided all round the 

 charcoal, and the observations were made both with the oven 

 kept tightly closed and with charcoal exposed to air currents 

 of regulated velocity. It was found that when flake charcoal 

 was heated in currents of air varying from five to sixty-two 

 cubic feet per minute, for one cubic foot of the charcoal, 

 ignition occurred at temperatures of 96° to 1 10° C, but that at 

 lower temperatures there were no indications of spontaneous 

 heating. 



Exposure of the charcoal to a current of air containing five 

 per cent, of sulphur dioxide caused spontaneous ignition to 

 take place in the course of a few hours. From these results 

 the conclusion is drawn that disinfection of a room by means 

 of sulphur dioxide may be attended with some risk of 

 spontaneous combustion when the walls contain charcoal. 

 There is much less chance, however, of decayed wood becoming 

 ignited in this way, as it does not take fire so readily as 

 charcoal. 



ARSENIC IN VEGETABLE PRODUCTS.— Since it has 

 been shown by MM. Gautier and Bertrand, that arsenic 

 occurs normallv in the tissues of man and of animals, various 



investigations have been made to discover the source of the 

 arsenic. Experiments made by MM. Stein, Gautier and 

 Claussmann have indicated that the arsenic probably 

 originates chiefly from vegetable foods, and its presence has 

 hitherto been detected in cabbages, potatoes, wheat and sorrel. 



This conclusion now receives confirmation from the experi- 

 ments of MM. Jadin and Astruc iCoiiiptes Reitdus, 1912, 

 CLIV. 893), who have made a systematic examination of 

 thirty-six difterent kinds of vegetable products, including fungi, 

 fresh and dried \egetables, cereals, nuts, and fresh and dried 

 fruits. 



In each case the arsenic was estimated by a modification of 

 Marsh's method, with all the usual precautions as to purity of 

 reagents and so on, and the results were expressed in 

 milligrammes per 100 grammes of material. 



Arsenic was present in varying proportions in every instance. 

 Thus, in the fresh vegetables it ranged from • 004 milHgramme 

 in peas to 0-02 J milligramme in lettuce, while the edible 

 portion of fresh fruits yielded from 0-005 milligramme 

 (chestnuts and apples) to 0-012 milligramme (mandarines). 

 Mushrooms contained 0-006 milligramme and truffles 0-020 

 milligramme. 



PURITY OF LONDON'S WATER SUPPLY. — The 

 Seventh Annual Report (for 1911) of the Metropolitan Water 

 Board gives further details of the researches of Mr. A. C. 

 Houston upon the vitality of pathogenic micro-organisms in 

 water. Various bacteria were added to samples of river 

 water, and cultivations made to ascertain how long they 

 survived. The results confirmed those previouslj' recorded, 

 and showed that typhoid bacilli did not survive more than 

 three weeks under these conditions, their vitality being thus 

 much lower than in the laboratory cultivations. 



Other experiments upon the river water as received showed 

 that it is exceptional for pathogenic micro-organisms to be 

 found in small quantities of the water. Out of seven thousand 

 nine hundred and ninety-one colonies examined, only one 

 micro-organism resembling the typhoid bacillus was found. 



From these results it would seem that storage of river 

 water for a month is practically sufficient to destroy all typhoid 

 bacilli. 



Lowering the temperature had a curious effect in prolonging 

 the life of typhoid bacilli added to river water, temperatures 

 below 41' F. being much more favourable to their survival. 

 Yet, even in the case of water chilled to the freezing point, 

 only one typhoid bacillus was aUve after a month. 



A marked improvement in the chemical and bacterio- 

 logical character of the river water was effected by a pre- 

 liminary storage for a day in small reservoirs, prior to its 

 being transferred into the main storage reservoirs. This 

 improvement was still further enhanced by treating the water 

 with a small proportion of an " alumino-ferric " coagulating 

 agent, on its way through the small reservoir. 



FERTILISING ACTION OF SULPHUR.— According 

 to M. A. Demolon Xoiuptes Rend.. 1912, CLIV, 524) residues 

 from the gas works are extensively used in the North of 

 France as fertilisers for the soil. Analyses of various samples 

 of the material showed that it contained about forty per cent, 

 of sulphur, and from one to three per cent, of nitrogen in the 

 form of ammonia or its salts. 



The value of the substance as manure was found to depend 

 upon the sulphur, and this conclusion was confirmed by 

 practical tests in which flowers of sulphur were incorporated 

 with garden soil. In every instance, the growth, both of the 

 roots and the leaves, was promoted, and the colour of the 

 plants was a deeper green. Apparently, the sulphur acts by 

 stimulating the formation of chlorophyll. A portion of it 

 becomes oxidised to sulphate in the soil. 



GEOLOGY. 



By G. W. Tyrrell, A.R.C.Sc, F.G.S. 



AUSTRALIAN GLACIATIONS.— W. Howchin writes 



on this subject in The Journal of Geology, April-May. 1912. 



.Australia has experienced three well-defined periods of glacia- 



tion in the Cambrian, Permo-Carboniferous and Pleistocene. 



