August 23, 1900] 



NA TURE 



391 



influence it. The discovery of this distinction overthrew all the 

 old ideas dating from antiquity, and which continued up to the 

 end of the last century. According to the idea? which were cur- 

 rent when Lavoisier started his work, there were four elements 

 — earth, air, fire and water — from which all substances existing 

 in nature were said to be built up. By associating these ele- 

 ments in different proportions and by different methods, it 

 ought to be possible to produce all bodies and transform any 

 one into any other. As a matter of fact, the prolonged re- 

 searches of serious workers had never succeeded in establishing 

 this transformation, nor has this been accomplished since. But 

 preformed ideas are tenacious, especially when supported by 

 mysticism. 



An equally grave mistake was committed in supposing that 

 bodies submitted to the influence of heat alone could vary in 

 weight, a variation apparently proved by innumerable observa- 

 tions with the balance in chemistry. It is, in fact, a most 

 singular error, although one frequently held, that the use of the 

 balance in chemistry dates only from the end of the last century. 

 In reality its use is sixteen centuries old. The balance was used 

 both in chemistry and in trade ; it may be seen represented on 

 the monuments of ancient Egypt. Bodiessuch as coal, oils and 

 organic substances under the action of heat were known to lose 

 their weight, hence was drawn the conclusion that matter may 

 be transformed into heat and disappear ; whilst heat, on the 

 other hand, under inverse conditions, could be fixed, becoming 

 visible ponderable matter. These opinions gave way to the 

 views of Stahl, according to whom combustible bodies were 

 rich in phlogiston, or fixed heat. Such was the state of science 

 about 1772, when Lavoisier appeared on the scene. Ten years 

 were sufficient for him to effect a complete transformation. He 

 established, by the most precise experiments, a fundamental 

 distinction, previously unknown, between the nature of bodies 

 which we know, and heat and other agents capable of modifying 

 these ; it is the distinction between ponderable bodies and the 

 imponderable heat, light, electricity, the intervention of which 

 causes no change of weight in ponderable matter. 



It could hardly have been expected that one man alone should 

 make all the researches establishing the properties of gases, the 

 composition of air and of hot water, and in this respect there 

 can be no doubt that Lavoisier profited by the partial work of 

 his predecessors and of contemporary workers ; but to him alone 

 belongs the merit of demonstrating the connecting links, and 

 of giving the facts their true interpretation. 



Two fundamental problems were first attacked by Lavoisier, 

 the gain in weight of metals on calcination, and the apparent 

 loss of weight of carbon, sulphur and oils on combustion. His 

 first discovery was to put these phenomena upon a proper ex- 

 perimental basis. He demonstrated that in all such cases a 

 weighable substance contained in the air takes part in the 

 change, the addition of which explains the increase of weight of 

 the calcined metals, an increase equal to the loss of weight sus- 

 tained by the air. The same ponderable element in the air was 

 shown to take part in the burning of carbon, sulphur and oils, 

 forming gaseous compounds, the weight of which was also de- 

 termined by Lavoisier. It was thus established, what had 

 never been done before, that the materials of bodies possessing 

 weight kept this weight constant throughout a series of chemical 

 changes, heat and other agents of the same order having no 

 effect either in increasing or decreasing the weight of the original 

 bodies. This fundamental distinction between ponderable 

 matter and imponderable agents is one of the greatest discoveries 

 that has ever been made ; it lies at the base of physical, chemical 

 and mechanical science. Lavoisier, however, went farther than 

 this, and attempted to penetrate the constitution of ponderable 

 matter itself. He recognised that in all known experiments it 

 presents itself as constituted by a certain number of unde- 

 composable elements or simple bodies, which, combining 

 amongst themselves, form ail known compounds. 



The two fundamental laws of nature once established— the 

 distinction between matter and imponderable agents, and the 

 invariability of the nature and weight of the simple bodies — 

 Lavoisier went on to draw important conclusions on the 

 composition of the acids and metallic oxides, the composition 

 of air, water and organic substances, on the rdle of heat 

 in chemistry, on animal heat and on the niture of respiration 

 in physiology. 



What share ought to bs now attributed to Lavoisier in the 

 classical discovery of the compound nature of air and water, a 



NO. 1608, VOL. 62] 



discovery in which he competed with Priestley and Cavendish ? 

 The matter would take too long to give here in detail. Suffice 

 it to say that he alone swept from the composition of air and 

 water the erroneous notion of phlogiston maintained by his 

 contemporaries. 



All these discoveries, accumulated in the course of only a 

 dozen years, and carried out with wonderful ardour and energy, 

 were not simple proofs of isolated facts ; on the contrary, they 

 were the consequences logically deduced and experimentally 

 demonstrated of the two fundamental laws due to the genius 

 of Lavoisier. The physiological questions relating to respira- 

 tion were also answered completely and successfully ; given a 

 correct knowledge of the elementary composition of carbonic 

 acid, of food materials and of air, respiration was then obviously 

 a slow combustion of food by the oxygen of the air, a com- 

 bustion producing carbonic acid and developing at the same 

 lime sufficient heat to maintain the human body at a nearly 

 constant temperature. 



A complete account of the after effect of Lavoisier's work 

 would require almost a history of physical science during the 

 nineteenth century ; but an attempt will be made to recapitu- 

 late the more immediate consequences upon existing knowledge. 

 The notion of the invariability of the weights of the simple 

 bodies dominates the whole of chemistry at the present time ; it 

 is the scientific basis of all our chemical equations of composition 

 and constitution, the origin of the new and singular algebra 

 which, from its origin in the vvorks of Lavoisier, so struck the 

 mathematicians of his time. It is also the solid foundation of 

 all our analyses, and is a certain starting-point in industries the 

 most diverse, the manufacture of acids, alkalis, colouring 

 matters, scents, drugs, in metallurgy and in agriculture. 



And here a necessary reflection occurs. It cannot be pretended 

 that Lavoisier was the direct and personal author of the vast 

 array of discoveries here enumerated ; but it is certain that it 

 is he who has established the solid base upon which the modern 

 chemical edifice is constructed, and without which these dis- 

 coveries could not have been made ; it is he who has raised the 

 flaming torch of truth which we daily invoke, and for that 

 reason it is just and equitable to give to him a part of the glory 

 of the inventions of science and modern industry. 



T' 



NILE FLOODS AND MONSOON RAINS. 



HE practice or science of weather forecasting will 

 evidently proceed on two very dififerent lines — 

 according to the relative importance of local or seasonal 

 changes in the general meteorological conditions, and 

 whether the prediction has reference to a long or a short 

 period. The machinery employed in cases where the 

 forecast aims at great minuteness over a small area 

 consists mainly of the synoptical chart, based on inform- 

 ation supplied by rapid telegraphic communication, and 

 in the hands of experts this means probably proves 

 sufficient, and furnishes a fair percentage of accurate 

 predictions. But in the more difficult, as certainly the 

 more important, problem of predicting the weather some 

 time in advance, and over a considerable area, a problein 

 which regularly recurs in the monsoon forecast for India, 

 one must evidently depend on the more general physical 

 conditions that are produced by the motions of the earth 

 and the distribution of land and water on its surface. 

 These causes, it is true, are always operative, and to a 

 certain extent ineteorological phenomena, broadly con- 

 sidered, must be periodic in their main features. The 

 causes of deviation from periodicity, and the extent of 

 the area afifected by such abnormal conditions, are prob- 

 lems which the professional meteorologist has to 

 encounter, and it is to be feared with insufficient means. 

 But it seems not unlikely that, in proportion as the 

 problem becomes more general, by bringing wider areas 

 within the scope of the discussion, the prospects of 

 greater success will become more assured ; and it cannot 

 but be considered a most significant feature that indica- 

 tions are not wanting that in the two considerable areas, 

 India and Egypt, the respective climates betray 



