June 5, 1919] 



NATURE 



271 



country. In the January-February issue of the 

 Bullettn de la Socidti d' Encouragement pour I'lndus- 

 trie Nationale some interesting details are given on the 

 manufacture of these stones or "flints," which are now 

 so well known to smokers in this country. Ferro- 

 cerium is an alio)- consisting, for the purpose under 

 discussion, of 30 parts of iron to 70 parts of cerium. 

 The raw material is derived from the monazite sands 

 of Brazil. These sands are enriched until the pure 

 monazite is obtained. They are then treated 

 chemically to extract the oxylate of thorium, phos- 

 phoric acid, and oxylates of' cerium, lanthane, and 

 didymium. The cerium oxylates are afterwards con- 

 verted into hydrates or carbonates, then into chlorides. 

 The chloride is finally electrolysed and decomposed 

 into its elements, chlorine and cerium, the electro- 

 lytic process being continuous. The pure cerium is 

 allowed to iron in the proportions mentioned above. 

 The two substances are placed in fire-clay crucibles, 

 w hich are heated to i ioa° C. by a gas furnace. When 

 the alloy is thoroughly liquid it is cast in moulds 

 formed by a series of several hundred sheet-iron tubes, 

 -: S mm. in diameter and 30 cm. long. These tubes are 

 allowed to cool in the air and then " stripped," i.e. they 

 iiave an opening down the side and the thin sheet- 

 iron is simply wound off the ferro-cerium, which is 

 left in the form of a thin rod. One kilogram of ferro- 

 cerium contains 5500 '" flints " of 5 mm. length, which 

 are each capable of giving some nine hundred flashes. 

 The French manufacturer who took up this industry 

 has also prepared other products of some importance, 

 e.g. thorium nitrate, which is being used in a special 

 type of incandescent lamps, and cerium, which is 

 being used for the manufacture of cerium steels. 

 This new application on the part of the French will 

 release them from the German tribute after the 

 war. 



M. L60N Appert, in the January-February issue of 

 the Bulletin de la Sociiti d' Encouragement pour 

 rindustrie Nationale, contributes a long and interest- 

 ing paper on the welding of glasses. He traces the 

 history of these, attempts from the earliest ages, and 

 considers the technical methods most l?kely to lead to 

 success. His conclusions are: — (i) That it is always 

 possible to weld together, completely and permanently, 

 glasses of different composition, whatever the con- 

 stituents of the glasses. {2) That the limits within 

 which the relative proportions of these constituents 

 may be varied are very close; and, to ensure success, 

 the modifications which may result must be carefully 

 borne in mind in practice, such as changes in the 

 quality of the products used, modifications in com- 

 position which may occur spontaneously, the tem- 

 perature at which fusion is carried out, and the dura- 

 tion for which this temperature is applied. (3) As 

 regards conditions of athermancy and diathermancy, 

 the most simple methods should be used for controlling 

 these conditions, a glass of known composition being 

 used as a standard and for purposes of comparison. 

 (4) As regards neutrality, direct experiments with the 

 blowpipe should be made. This kind of test, which 

 is very simple to carry out, gives at the same time 

 information on the greater or less fusibility of the 

 glass, and on the consequences arising out of the 

 use of a variable temperature, which may sometimes 

 be too high or applied too long. (5) .As regards the 

 welding of enamels with metals, ' the question of 

 adhesion being of the first importance, care should 

 be taken over the qualities of the mordant, which 

 must have the same dilatation coefficient at the out- 

 -<n, and at the same time be capable of attacking the 

 underlying metal with the view of multiplying the 

 points of adhesion. (6) The enamel should be em- 



NO. 2588, VOL.. 103] 



ployed only in as thin layers as possible and by suc- 

 cessive applications. If these conditions are observed, 

 the success of the operation of welding may be 

 regarded as ensured. 



In the Journal of Agricultural Research for 

 December 2 last, Messrs. True and Geise give an 

 account of a series of pot exp>eriments carried out to 

 determine the value of greensand (glauconite) deposits 

 as a source of the potassium required by growing 

 plants. Potassium is a normal constituent of glau- 

 conite ; the question was whether in this silicate it 

 is present in a sufficiently soluble form to be utilisable 

 by the plant. In the result it was found that green- 

 sands and greensand marls from Virginia and New- 

 Jersey were able to supply sufficient potassium to 

 meet the demands of wheat and red clover during 

 the first two months of growth, i.e. at the time when 

 the absorption of potassium is greatest. The plants, 

 in fact, made a greater weight of "tops" than was 

 found in similar cultures where the potassium re- 

 quirements were supplied by means of the chloride, 

 sulphate, and phosphate. The authors conclude that 

 the deposits mentioned can apparently furnish avail- 

 able potassium to meet the needs of many farm crops, 

 and perhaps of most. 



A NEW form of ship's rudder, invented by Mr. 

 J. G. A. Kitchen, of Lancaster, forms the subject of 

 an article in Engineering for May 16. The invention 

 permits the boat to be steered, reversed, controlled in 

 si>eed, and manoeuvred in any way from a single 

 tiller, with the engines running continuously at full 

 speed in the forward direction. Complete and direct 

 control is obtained by the steersman over all move- 

 ments during manoeuvring, and all engine-reversing 

 gear may be eliminated. Two curved deflectors form- 

 mg parts of a circular cylinder partly enclose the 

 propeller. The deflectors are pivoted at the top and 

 bottom on common centres, and are capable of being 

 swung together in the same direction, or equally in 

 opix)site directions. .\ graduated opening or no open- 

 ing is thus provided for the stream of water leaving 

 the propeller; in the case of no opening, the entire 

 stream of water is deflected forwards, and the boat 

 moves astern. There is a neutral position of the de> 

 flectors in which the boat remains at rest with engines 

 working at full speed. The operating gear is exceed- 

 ingly simple, so that even a novice acquires complete 

 command over the boat's movements after a few- 

 minutes' practice. Many of the Admiralty pinnaces, 

 etc., driven by oil-engines have been fitted during the 

 war, although publication of particulars has been 

 hitherto prevented. The following gives some idea of 

 the importance of the device, and relates to trials of 

 a 25 ft. launch belonging to the Air Ministrv-. Ahead 

 speed, g-8o knots ; astern speed, 3-5 knots (suflRcient 

 for all requirements). Full speed ahead to dead stop : 

 boat pulled up in 16 ft. (one man aboard). Time of 

 turning- through a complete circle, without pro- 

 gression in any direction : to starboard, 33 sees. ; to 

 port, 26 sees. The results for several other boats are 

 given, and are equally good. 



The statement in a letter in last week's Nature 

 that Messrs. Newton and Wright, Ltd., produced 

 interrupterless machines before "any .American firm" 

 had done so should have read " anv other .American 

 firm." The word "other" was inadvertentlv omitted 

 from the sentence. Mr. Snook's ow-n factorv was the 

 first to place a practical machine on the market, and 

 Messrs. Newton and Wright, Ltd., were the first on 

 this side of the .Atlantic. 



