I30 



NATURE 



{Jtme 1 8, 1874 



are already situated above the anthers before the opening 

 of the flower. 



Whilst in ^Tyosurus miniiinis %A{-{tx\S!d%7X\ovi. is effected 

 by a number of stigmas passing along each of the 

 anthers, Myosotis Vt'rsicolor attains the same effect in 

 the contrary way, all five anthers of the flower passing 

 along the single stigma. 



The corolla, when opening, is not only still of a pale 

 yellowish colour, like the buds of other species of Myo- 

 sotis, but even when not yet fully developed the anthers 

 and pistils are mature at the same time and the stigma 

 slightly overtops the corolla. Hence when insects visit the 

 flowers in this state, their probosces always touch the 

 stigma sooner th?n the anthers, and consequently, when 

 flying to another flower, always cross-fertihse it. 



But by the gradual lengthening of the corolla-tube the 

 anthers aftixed to its inner side are raised till they sur- 

 round and self-fertilise the stigma now enclosed in the 

 corolla (Fig. 40). Thus also in this inconspicuous flower 

 the defective cross-fertilisation by insects * is largely 

 supplied by regular self-fertilisation. 



Hermann Muller 



INTERNATIONAL MET-RIC COMMISSION 



A T PARIS 



Melting of the Metal for the new Metric Standards 



AT the meeting of the Executive Committee of the 

 International Metric Commission in October last, 

 the fusion of the large single ingot of platinum-iridium, 

 weighing 250 kilogrammes, out of which all the new 

 metric standards were to be constructed, was fixed for 

 the end of the following April, but the completion of the 

 operation was delayed by accidental circumstances until 

 the middle of the following month. As this was the first 

 occasion on which any attempt had ever been made to 

 melt together more than a few kilogrammes of platinum 

 or of platinum alloyed with iridium, it w-as necessary to 

 make a great number of experimental meltings during 

 the intermediate time in order to secure success in the 

 great operation. 



All the actual meltings of the platinum and iridium 

 have been made at the Conservatoire des Arts ct Metiers, 

 in a building erected for the purpose. The work has 

 been carried out under the superintendence of M. Tresca, 

 the Sous-Directeur of the Conservatoire, who is also 

 honorary secretary of the Commission, and more imme- 

 diately intrusted with the technical operations of con- 

 structing the nev/ standards. He has had the advantage 

 of the cordial assistance of Mr. George Matthcy, of the 

 firm of Johnson and Matthcy, Hatton Garden, from 

 whom the large mass of platinum and iridium was 

 obtained. Mr. G. Matthey has had large personal expe- 

 rience in melting platinum, and he remamed at Paris 

 from the beginning of April assisting in the work. 



It was necessary that the whole of the platinum and 

 iridium should be separately assayed and purified pre- 

 viouslv to their being melted together. This process 

 was entrusted to M. Henri Sainte-Clairo Deville, and 

 carried out at the Ecole Normale, of which he is 

 director. The greatest difficulty in the purification con- 

 sisted in getting rid of the osmium, which is found in the 

 natural ore in combination with platinum and with iri- 

 dium. But the chemical difficulty was satisfactorily over- 

 come by M. Deville after many experiments made by 

 him. 



The whole of the platinum and iridium had thus been 

 ascertained to be perfectly pure when delivered to M. 



* After having repentedly watched in vain the flowers of Myosotis versi- 

 color, I succeeded twice ni seeinp it fertilised by insects, viz. — May 15, 

 1873, 1 observed Boiiihiis asnruin V. ? , and June 2, 1871, Ilntictus srxiw- 

 talus K. 9 , //. zoniilus Sm. 9 . Rhiiigin rostrata L. , and Syriltu /-i/ieiis L., 

 all of them successively sucking flowers of different steins. Rut certainly by 

 far the greatest part of all the flower remains without any visit of insects. 



Tresca for melting. The first process was to melt por- 

 tions of the pure platinum, its melting point being about 

 1,900° C, and considerably lower than that of iridium, 

 which is about 2,400° C. Portions of the platinum were 

 then remclted together with iridium, in the proportions 

 fixed upon of 90 per cent, of platinum and 10 per cent, of 

 iridium. Quantities of from 10 to 15 kilogrammes of 

 platinum-indium were, in the first instance, melted to- 

 gether. Several of these smaller ingots were then re- 

 melted into larger ingots of rather more than 80 kilo- 

 grammes each, and the final operation was to remelt 

 three of these larger ingots into a single ingot of 250 

 kilogrammes. 



Each of the meltings was made as nearly as possible 

 of uniform form in a furnace heated with oxy-hydro- 

 gen gas. The furnace was made of a block of the ordi- 

 nary sandy limestone used for buildings in Paris. For 

 the smaller ingots a square block of stone was employed 

 with a hemispherical cavity about 6 in. (15 centimetres) 

 in diameter, for containing the metal. This small block 

 had a cover of similar form, and through its middle was 

 a vertical hole, about 2 in. in diameter, in which the tube 

 for conveying the gas was fixed with mortar. When the 

 metal was placed in the furnace, and the jet of lighted 

 gas directed upon it, sufficient mortar was placed on the 

 joining of the upper and lower blocks of stone to make it 

 air-tight. For the three larger ingots a long oblong fur- 

 nace was used, with a cavity of the same breadth, but a 

 little deeper and much longer, and three gas-tubes were 

 used. The largest furnace required for the whole quantity 

 of metal had six gas-tubes, each about i in. in diameter, 

 inserted in the upper block. The ordinary illuminating 

 gas was used, mixed with the requisite proportion of 

 oxygen gas, made on the premises and stored in a large 

 gasometer placed near the furnace room. For obtaining 

 a sufficient blast the power of a 15-horse steam-engine 

 was employed. 



In order to facilitate the melting, it was necessary first 

 to divide the larger ingots into small pieces. About half 

 the quantity for a single melting, thus divided into small 

 lumps, was placed in the mould, and when this was com- 

 pletely melted the remainder, which had been drawn out 

 into long thin bars, was introduced gradually through two 

 small holes opposite each other in the furnace. These 

 holes also enabled the interior of the furnace to be seen, 

 together with the progress of the melting, and they could 

 be closed by stone plugs when requisite. The division 

 of the ingots was a difficult operation, as this alloy of 

 platinum and iridium is harder than ordinary steel. A 

 V cut, about J in. deep, was made around the ingot with 

 a cold chisel, though not without splintering the edges of 

 a considerable number of the best-tempered chisels. 

 The ingot was then placed under a hydraulic press, sup- 

 ported upon the rounded tops of two strong iron bars, a 

 sufficient distance apart. The rounded part of a third 

 bar was placed upon the ingot, in the line of the cut, and 

 the power of the press being applied, the ingot was broken 

 in half, presenting in every instance a regular crystallised 

 grain. 



The melted metal was not cast into a separate mould, 

 but was allowed to cool in the furnace. During the 

 melting a portion of the interior of the stone, to the depth 

 of about half an inch, became coloured by the excessive 

 heat and formed into lime in a powdery state, which 

 fioated on the surface of the melted metal. When the 

 metal was sufficiently cool, the stone mould was broken and 

 the ingot removed to a bath of hydrochloric acid, which 

 dissolved every portion of lime or other foreign matter 

 upon the surface of the ingot, but does not act upon 

 platinum-iridium. The ingot was then left quite clean 

 and pure. 



The first of the larger ingots of 80 kilogrammes was suc- 

 cessfully melted on April 25. The second was melted on 

 May I, when Marshal MacMahon, the President of the 



