200 



NATURE 



\yan, 4, 1877 



A telephone — showing clearly the principle of the 

 apparatus — was exhibited by the Messrs. Wray, and 

 musical notes were accurately transmitted by means 

 of it through about 120 feet of wire. The battery 

 employed for the purpose was the thermopile, designed 

 by themselves, which was also shown. Although at 

 first sight very similar to the well-known form of Cla- 

 mond, the thermopile of Messrs. Wray has several modi- 

 fications which are undoubted improvements. The 

 extreme brittleness so fatal to many of Clamond's bars is 

 here got rid of by the introduction, for a distance of about 

 two inches, into the alloy, of a tongue which really is only 

 a continuation of the sheet-iron. At first sight one would 

 be inclined to think that this would tend to lower the 

 electro-motive force of the couple, but the reverse is stated 

 to be the case. The asbestos rings are replaced by a 

 framework composed of circular plates of earthenware 

 supported on three tie rods which serve to give stability 

 to the structure and remove from each ring of bars the 

 superincumbent weight of all the others over it. But per- 

 haps the main improvement effected is the method of 

 heating the bars ; instead of allowing the flamers to im- 

 pinge directly on their ends, or admitting the products of 

 combustion near them, an earthenware cylinder forms the 

 centre of the pile. Around it and abutting hard upon it 

 the bars are placed, and from a perforated chimney 

 within the gas issues, and burning in blue jets, speedily 

 raises the cylinder to a red heat, which is transmitted 

 through to the ends of the bars, 



THE PHYLLOXERA AND INSECTICIDES 



SOME time ago we published in our columns a short 

 account of the results of the investigations of various 

 scientific men in France into the nature of the Phylloxera 

 — that terrible scourge which is committing such wide- 

 spread ravages among the French vineyards. Latterly 

 we have received some reports communicated to the 

 French Academy of Sciences dealing with the attempts 

 which have been made during the last three or four years 

 to arrest the mischief done by the insect, and ultimately 

 TO destroy it altogether, by means of some potent drug. 

 It is obvious that the remedy to be employed must possess 

 two qualities at starting, viz., it must destroy the insect 

 and it must not damage to any great extent the vine. 

 But, further, it is not sufficient that when put in close 

 contact with the roots of a plant— as in a pot — it should 

 prove fatal to the insect, it is necessary, if the remedy is 

 to be of real practical value, that it should reach and 

 destroy the Phylloxera on all the parts attacked by it in 

 vines which are planted out in the open air. This is a 

 real difficulty to overcome, as the remedy, be it in the 

 form of solution or of vapour, cannot easily permeate the 

 soil, sometimes clayey, sometimes sandy, on which the 

 vine is growing, so as to reach and act upon the smaller 

 root branches whose nutrition the Phylloxera diverts into 

 itself. 



M. Mouillefert, a professor at the School of Agricul- 

 ture at Grignoii, was the gentleman delegated by the 

 Academy of Sciences to make the necessary experi- 

 ments for the purpose of determining what agent was the 

 most practically applicable to the destruction of the Phyl- 

 loxera, and the account of the numerous substances em- 

 ployed by him with varying results fills no less than 200 

 iiages of a memoir presented to the Academy of Sciences. 

 It is not our intention here to do more than give a brief 

 resume of the results at which he arrived. 



He divides the substances used by him into seven 

 f^roups, the first of which was composed of manures of 

 various kinds, such as guano, superphosphates, farm- 

 muck, &c. ; the second of neutral substances, as water, 

 soot, and sand ; the third of alkalies, as ammonia and 

 soda ; the fourth of saline products, amongst which were 

 the sulphates of iron, copper, zinc, potassium, and am- 



monia, alum, and sea-salt ; the fifth of vegetable essences 

 and products, as decoctions of hemp, datura, absinthe, 

 valerian and tobacco ; the sixth of empyreumatic pro- 

 ducts ; and the seventh of sulphur compounds. It was 

 only with some of the substances contained in this last 

 group that really satisfactory results were obtained, and 

 it is to M. Dumas, the permanent secretary of the French 

 Academy of Sciences, that the credit is due for suggesting 

 the employment of the alkaline sulpho-carbonates of 

 potassium and sodium and those of barium and calcium. 

 All the other classes of remedies mentioned above were 

 either without effect on the Phylloxera, or, in destroying 

 it, also destroyed or damaged the vine. 



The sulpho-carbonates, which were carefully studied 

 by the great Swedish chemist Berzelius. are obtained by 

 combining the alkaline mono-?;ulphides with the bi- 

 sulphide of carbon, are either liquid or solid, and emit a 

 powerful odour of sulphuretted hydrogen and bi-sulphide 

 of carbon. 



The alkaline sulpho-carbcnates in the solid state are of 

 a beautiful reddish yellow colour and deliquescent, but 

 are not easily obtainable in that condition ; the sulpho- 

 carbonate of barium can be easily procured, however, in 

 a solid state, and presents the appearance of a yellow 

 powder, but little soluble in water. The sulpho-carbonates 

 decompose under the influence of carbonic acid, forming 

 a carbonate, and evolving sulphui-etted hydrogen and bi- 

 sulphide of carbon. These two latter substances are 

 gradually liberated and, as they have a very powerful 

 effect on the Phylloxera, one can understand that the 

 sulpho- carbonate, placed in the ground, may prove, by its 

 slow decomposition, a powerful insecticide. In the case 

 of the sulpho-carbonate of potassium, over and above its 

 toxic effect, it has a direct invigorating influence upon the 

 vine, as the carbonate of potassium is an excellent 

 manure. 



The employment of the sulpho-carbonates as a means 

 for the destruction of the Phylloxera was suggested to M. 

 Dumas by the clearly-recognised need that there was of 

 some substance that would evaporate less quickly than 

 the bi-sulphide of carbon ; he saw that it was desirable 

 to apply the insecticides in some combination which would 

 fix them and only allow them to evaporate gradually, so 

 that their action might continue long enough in any one 

 place to infect with their vapours all the surrounding soil. 



But the task of eradicating the Phylloxera has by no 

 means been accomplished by the mere discovery of the 

 value for the purpose of these substances ; there is the 

 further difficulty of applying them to the vine in cultiva- 

 tion. One thing seems very certain, that in order to 

 render the sulpho-carbonates practically efficacious in kill- 

 ing the insect, it is necessary to use water as the vehicle 

 by which they may be brought to all the underground 

 parts of the plant, and that the best time of year for their 

 application is the winter or early spring, when the earth 

 is still moist and the quantity of water necessary to be 

 brought on to the ground by artificial means is conse- 

 quently less. Mixed with lime in the proportion of 2 to i, 

 these sulpho-carbonates give a powder which can be 

 spread over the ground before the heavy rains, that is, 

 between October and March, and which will probablj" 

 prove itself very efficacious. 



The conclusion at which M. Mouillefert arrives at the 

 end of his report is that the efficacy of the sulpho- car-j 

 bonates is proved, and all that is necessary is to bring tc 

 perfection their employment in agriculture, which car 

 only be accomplished by the intelligence and practica 

 knowledge of the vine-grower who is well able to dis- 

 cover the economic processes of culture which are con- 

 ducive to their successful apphcation. 



He ends by saying that " Science has accomplished its 

 mission, and it remains for Agriculture to fulfil its part " 

 in the eradication of the Phylloxera from the vineyards o£ 

 France. 



