128 



NA TURE 



[June 7, 1900 



have been published in the local papers. The bamboo forests 

 of Chanda consist of Dendrocalamus strictus, the male bamboo, 

 a bushy plant from 20 to 30 feet in height, and affecting the 

 cooler northerly and westerly slopes of Central and Southern 

 India. This is said to be the first time in the history of these 

 forests that a sweet and gummy substance has been known to 

 exude from the trees. The gum has been exuding in some 

 abundance, and it has been found very palatable to the natives 

 in the neighbourhood, who have been consuming it as a food. 

 The occurrence of the manna at this season is all the more re- 

 markable, since the greatest famine India has known is this year 

 visiting the country, and the districts where the scarcity is most 

 iceenly felt are in the Central Provinces. 



An authentic specimen of this Ijamboo manna was sent to 

 Dr. Watt, Reporter on Economic Products, Calcutta, and was 

 subsequently handed to me for examination. It occurred in 

 short stalactiform rods about an inch long, white or light brown 

 in colour, more or less cylindrical in shape, but flattened or 

 grooved on one side where the tear had adhered to the stem. 

 It was pleasantly sweet, without the peculiar mawkish taste of 

 Sicilian manna (Fraxinus rohindifolia). It was soluble in less 

 than its own weight of water, and the solution when allowed to 

 repose deposited white, transparent crystals of sugar. The 

 manna contained 2 "66 per cent, of moisture, 0"96 per cent, of 

 ash, 075 per cent, of a substance reducing Fehling solution, 

 and a small quantity of nitrogenous matter. The remainder 

 consisted of a sugar which became inverted in twenty minutes 

 when boiled with dilute hydrochloric acid (i percent.), and 

 from its solubility, melting-point and crystalline nature, appeared 

 to be a saccharose, related to, if not identical with, cane sugar. 

 It contained no mannite, the saccharine principle peculiar to 

 true manna. 



The bamboos and sugar canes belong to the same natural 

 order of grasses, and perhaps it is not unnatural to expect them 

 to yield a similar sweet substance which can be used as a food ; 

 but it is a coincidence that the culms of the bamboo, hitherto 

 regarded as dry and barren, should in a time of great scarcity 

 ■afford sustenance for a famine-stricken people. 



Indian Museum, Calcutta, May 3. David Hooper. 



Solution Theory Applied to Molten Iron and Steel. 



I AM pleased to notice that the theory of solution of iron and 

 steel has recently received attention, and that valuable work has 

 been placed before us for consideration by Baron von Juptner 

 (see recent proceedings of the Iron and Steel Institute). 



Will you, however, permit me to state that many years ago, 

 in a contribution to the Institute (/;-<?« and Steel Inst. 1881), 

 I advocated the theory of solution in the following words : — 



"The solution theory is directly applicable to fluid iron and 

 steel, as it is to water. Carbon, phosphorus, &c., are more or 

 less soluble in the fluid metal, just as salts are soluble in water ; 

 in both cases the same forces are at work ; water, however, at 

 the normal temperature of 60° Fahr., fluid iron about 2500°- 

 3500° Fahr." 



" Further, the physical or gaseous theory of solution best ex- 

 plains the facts ; the so-calied chemical theory of solution is 

 not so applicable. It is difficult to give satisfactory reasons for 

 the union of stable bodies such as carbon and iron, but the 

 gaseous theory of solution apparently does so. 



" The difficulty of its complete or further application becomes 

 one of degree only, for no definite distinction can be drawn be- 

 tween gases, liquids and solids, more especially when the latter 

 are heated. 



" The quantity of matter dissolved in a given time is simply a 

 function of temperature, and at low osmotic pressure is com- 

 parable with that of a liquid evaporating under the pressure of 

 its own vapour" (Nature, 1892). 



"Moreover, it is remarked that ordinary soft steels for sheets, 

 rails, &c. , should be so manipulated as to produce a colloid, or, 

 as near as possible, a non-crystalline material, avoiding always 

 the formation of large crystals" {Iron and Steel hist. 1881). 



In my practice I have always adhered to the solution theory, 

 finding that it gave the key to the solution of many discrep- 

 ancies observed in the manufacture of steel, which ordinary 

 analysis, and the usual theoretical deductions therefrom, some- 

 times failed to explain. 



It appears to me, however, that the solution theory requires 

 •pension. We have, I think, up to the present only touched 

 upon the surface of the matter, and more extended and deeper 



NO. 1597, VOL. 6 2] 



research will amply repay those who have already done work in 

 this direction. 



In connection with this subject, although perhaps not exactly 

 bearing upon it, there is what may be termed the theory of the 

 crystallisation of steel and iron. A sheet of ice, as is well 

 known, shows, when heated, beautiful structural, or more 

 correctly crystalline, changes. Why should not a steel plate 

 exhibit changes of this kind if similarly treated ? 



It is evident, as has been remarked of others, that if the sheet 

 of either ice or iron be suddenly cooled at a given temperature, 

 the structure or grain at that temperature will be approximately 

 retained, and that steel of a given chemical composition may 

 give a material of varying physical properties practically 

 governed by the applied temperature, but not, strictly speak- 

 ing, in accordance with its chemical composition, as usually 

 assumed. 



I have lately found that this happens, and have produced steel 

 of four degrees of hardness by mere temperature manipulation, 

 with metal containing only one-tenth per cent, of carbon to 

 gether with low per cents, of sulphur and phosphorus. I 

 believe also that this has been done to a certain extent by 

 others, but the facts have not, so far as I know, met with the 

 attention of the practical manufacturers of steel. 



Newport, Mon., May 16. John Parry. 



THE BACTERIAL TREATMENT OF 

 SEWAGE. 

 'X*HE discovery made by Schwann, in 1839, that a 

 -*• putrefying liquid swarmed with microscopic living 

 organisms, gave occasion to a long series of remarkable 

 investigations as to the general nature and the life-history 

 of these organisms, and the chemical changes which they 

 produced. 



Prominent amongst the names of those who prosecuted 

 these investigations stands that of Pasteur, who, in 

 1857, drew attention to the nature and causes of 

 fermentative changes produced upon sugar solution, of 

 the putrefactive changes in liquids containing animal 

 substances, and of disease changes in the blood of the 

 living animal, which were produced in the presence of 

 various minute living organisms. He showed that, if 

 these liquids were sterilised by heat, and were then duly 

 protected against receiving solid particles from the air, 

 or from other sources, these changes did not occur ; and 

 that contact with air which had passed through a red-hot 

 tube, or had been filtered through a cotton-wool plug, 

 was incompetent to introduce the organisms and to start 

 the above changes. 



These researches drew attention to the important part 

 played by the air as a vehicle of the organisms or of their 

 spores, and was supplemented by the researches of 

 Tyndall (1876), who proved that air vvhich had been 

 allowed to remain at rest until its motes had subsided was 

 incompetent to produce putrefaction. Tyndall also 

 proved that boiled sterilised broth, when opened'in Alpine 

 air, did not usually putrefy, and that the air near the earth's 

 surface in different localities, and even in the v same 

 locality at different times, possessed infective power 

 varying from nil to something considerable. The infer- 

 ence is that the distribution of these organisms and of 

 their spores varies very considerably in any horizontal 

 plane near the earth's surface. 



Percy Frankland (1886) determined the number of 

 these living organisms which could be developed from 

 equal volumes of air collected at varying heights from 

 the earth's surface. He made use of hills and cathedral 

 towers for the purpose of collecting his samples, and 

 noted a regular decrease in the number of the organisms 

 which were in the air at greater and greater distances 

 from the earth's surface. 



These typical researches render it evident that the 

 organisms and their spores, which are produced at or 

 near the earth's surface, are wafted by natural atmo- 

 spheric movements to some height, but are constantly 



