NA TURE 



[May 9, 1 90 1 



As my principal object in these researches had only been to 

 get rid of the carbon spectrum (thouf;h in vain), I did not make 

 any measurements of wave-length. Later on, as many labora- 

 tories were provided with powerful spectroscopic apparatus, I 

 did not believe it to be any longer worth while to work on the 

 subject with small instruments, hoping some other investigator 

 would take care of it. I should be very glad if the present note 

 would induce some spectroscopist to control and further pursue 

 my observations. In addition, some researches with very strong 

 sparks seem to me to be very desirable. 



Berlin. Karl v. Wesendonk. 



The Dust of "Blood-Rain.'' 



I HAVE handed to Prof. Judd the specimens of " blood-rain "' 

 dust collected by me in Sicily, as mentioned in your issue of 

 March 2S. It may be remembered that the dust was collected 

 from three tables on the terrace of the hotel, and that I brought 

 home that from the most favourably situated table in the wet 

 state in which it was obtained. This has since been dried and 

 weighed, with the result that, as I expected, the density of the 

 fall was greatest on this table, being equivalent to 9-I tons per 

 square mile. The average given by the other two tables was 

 54 tons per square mile. 



The largest value is probably the best, but if we take the 

 mean we shall be within the mark in saying that the density 

 of the fall near the theatre at Taormina was about 7 tons to the 

 square mile. Arthur W. Richer. 



A Convenient Primary Cell. 



In your " Notes" of April iS (p. 594) you give an account of 

 the new cell — theCupron-element — brought out by the Accumu- 

 lator Industries Company. Without intending any disparagement, 

 will you allow me to point out that the cell, with the exception 

 of the special form of copper oxide for which the company justly 

 claim credit, was invented long ago by Lalande, but does not 

 appear to be known so widely as its merits deserve. I have 

 used the cell for a considerable time, the positive plate taking 

 the form of a plate of copper faced on one side with granular 

 copper oxide held in its place by a piece of copper gauze, and 

 can corroborate the statements as to its very low resistance and 

 great constancy. For elementary work, where resistances of a 

 few hundredths of an ohm are to be compared and a galvanometer 

 of negligible resistance used, I have found it most valuable. 

 Another form of the cell, in which the copper plate is merely 

 painted with a mixture of copper oxide powder and gum and 

 then heated until the latter chars, is very readily set up, but has 

 a rather greater internal resistance. Where this is desirable it 

 may be regulated within considerable limits by making the cell 

 a "sawdust Lalande," which has obvious advantages on other 

 grounds. A. E. Mu.nbv. 



Felsted. 



Through the kindness of the Editor I am able to reply to 

 Mr. Munby's interesting letter. I did not intend by my note to 

 imply that the " Cupron-element " was an entirely new com- 

 bination, and indeed suggested that its chief claim to novelty 

 lay in the construction of the copper oxide plate. The Accu- 

 mulator Industries, Ltd., it is only fair to say, fully acknowledge 

 in their circular that the cell is developed from the copper oxide 

 element of Lalande and Chaperon. It is interesting to have 

 Mr. Munby's testimony to the convenience of the cell, which is, 

 I believe, used to a considerable extent on the Continent, but, as 

 your correspondent says, is not very widely known in England. 

 The Writer of the Note. 



AGRICULTURAL SEEDS. 

 T T NDER the auspices of the Board of Agriculture a 

 ^ committee was appointed last summer to take into 

 consideration the conditions under which agricultural 

 seeds are at present sold, and to report whether any 

 further measures can, with advantage, be taken to secure 

 the maintenance of adequate standards of purity and 

 germinating power. 



The committee met on ten occasions and examined 



upwards of thirty witnesses, seed-merchants, farmers 



and scientific witnesses, including Mr Carruthers, Mr. 



Gilchrist, Mr. Hall, Profs. T. Johnson, McAlpine and 



NO. 1645, VOL. 64] 



Somerville. The evidence of these witnesses is now 

 published as a Blue-book, whilst the report of the 

 committee is issued separately. 



Taking the report first, the committee find that there 

 is [now] no wide-spread complaint of the quality of seeds 

 sold throughout the country. The cominittee, further, 

 think that every encouragement should be given to seed- 

 merchants to give a guarantee with the seeds they sell, 

 and that farmers should be advised to buy only subject to 

 such guarantee and to test the seeds they have purchased. 

 To facilitate this the committee recommend the establish- 

 ment of one central seed-testing station under Govern- 

 ment auspices, with the aid and counsel of a small 

 committee of experts. The report is signed by all the 

 members of the committee. Two of their number, Sir 

 VV. T. Thiselton-Dyer and Mr. Leonard G. Sutton, while 

 agreeing generally with the findings of the committee, 

 raise objections to the proposal to establish a Govern- 

 ment seed-testing station. 



It is satisfactory to hear that the general quality of the 

 seeds sold has greatly improved of late years. This 

 improvement is, no doubt, in great measure due to the' 

 passing of the Adulteration of Seeds Act, an Act, it may 

 be pointed out, which was promoted by the seedsmen 

 themselves, who desired to purify their business from 

 seed-killing, seed-dyeing and other questionable practices 

 which had been allowed to grow up to such an extent 

 that it was difficult for a merchant to avoid conniving 

 at, if not practising them. 



At present, so far as the large firms are concerned, 

 there is in general no question as to the excellence of the 

 seeds they sell, and those who, like the writer of the 

 present notice, have had the opportunity of witnessing 

 the care taken in selecting the seed and in afterwards 

 cleaning it and preparing it for market will corroborate 

 this statement. With the smaller dealers, especially in 

 some parts of Wales and Ireland, the case seems different. 

 There the farmers often buy relatively small quantities of 

 seeds of low quality and equally low price from local 

 tradesmen, ironmongers, cornfactors and the like, who 

 have no other knowledge of seeds than such as is 

 necessary for securmg the best means of disposing of 

 them. It is especially for the protection of small, and 

 often ignorant, farmers that the seed-testing station is 

 intended. 



All the large firms test their own seeds and the seeds 

 they buy from the Continent or elsewhere. Moreover, 

 they grow them in their own trial grounds. They do this 

 on a very much larger scale than would be possible in 

 a seed-testing station. 



Some of the smaller firms, and perhaps some of the 

 large houses also, occasionally make use of the seed- 

 control stations at Zurich or Halle, and they find it a 

 grievance that they have to send to Switzerland or 

 Germany for information which obviously could as well 

 be obtained here. Indeed, the botanists of the Royal 

 Agricultural .Society (Mr. Carruthers) and of the High- 

 land and Agricultural Society of Scotland (Mr. McAlpine), 

 and perhaps others, do undertake to test seeds for the 

 members of their several societies, or, under certain 

 conditions, for outsiders. 



These tests, wherever they be made, have reference to 

 the " purity " of the seed, its germinating power and its 

 "genuineness." By purity is meant freedom from seeds 

 of weeds or other admixtures. The germinating power 

 is tested by the percentage of seeds in any given sainple 

 which, under favourable conditions, is found to produce 

 healthy seedlings. Theoretically a hundred per cent, 

 should grow. In practice the percentage may, without 

 fault of the seedsman, be, in certain cases, much below 

 this, but it is satisfactory indeed when one thinks of the 

 many contingencies to which the clover plant is subjected 

 to find it to be quite common for 98 per cent, of the seed 

 to grow. When one thinks of the humble bees, and the 



