598 



NA TURE 



\ April 2'i, 1 88 1 



furnace. In 1838 he proved, by accurate analyses of the 

 gases escaping, " that at least 42 per cent, of the heat 

 evolved from the fuel employed is lost, and that in view 

 of the ease with which such combustible gases can be 

 collected and led off to a distance for subsequent use, a 

 new and important source of economy in the iron manu- 

 facture is rendered possible." This research is however 

 not only noteworthy as pointing the way to a method of 

 economical working without which piobably but few iron- 

 masters at the present day could e.Kist, but also as being 

 the first experiment in which an accurate method of gas- 

 analysis was employed. This important branch of ana- 

 lytical chemistry has been created and brought to its 

 present wonderful degree of precision solely by the head 

 and hands of the Heidelberg experimental philosopher. 

 Simplicity and accuracy constitute the rare merits of 

 Bunsen's system of gaseous analysis. To have gone 

 completely through his course of gas analytical manipu- 

 lations from the sealing-in of the platinum wires in the 

 eudiometer to the absorption- and e.xplosion-analyses of 

 the Heidelberg coal-gas, under the eye and with the 

 guilding help of the hand of the master, is in itself an 

 experimental education of no mean order. But it is only 

 on reference to his " Gasometric Methods " that we learn 

 the general adaptabihty of this marvellously accurate 

 system to all those numerous problems in which the 

 analysis of a mixture of gases is required. 



Next in order (1S41) comes the invention of the Bun- 

 sen batter)', an invention which has proved of the greatest 

 practical value to mankind, inasmuch as this form of 

 battery is now very largely used all over the world, not 

 only as a scientific instrument, but also for ordinary tele- 

 graphic purposes. The chief pomt in this invention con- 

 sists in the employment of carbon as the negative pole 

 in place of copper or platinum. In bis first communica- 

 tion on this subject, Bunsen accurately measures the 

 absolute intensity of the current from his zinc-carbon 

 battery, and compares it with that of a Grove (zmc- 

 platinum) battery, invented a short time before by Sir 

 William Grove. 



Bunsen's next great achievement consists in the in- 

 vestigation from both the chemical and the physical 

 point of view of the volcanic phenomena of Iceland. 

 The several memoirs on this subject are the result of a 

 visit to Iceland in 1847. They consist, in the first place, 

 of a careful and extended series of analyses giving the 

 average composition of the volcanic rocks of different 

 ages occurring in the island, upon which he founded a 

 most important and very general theory of volcanic action, 

 a theory which he has since proved is applicable to the 

 formation of other volcanic rocks of widely different origin, 

 both as regards time and locality. This theory consists, 

 to begin with, in a proof that all the Islandic rocks, of 

 whatever age, may be considered as mixtures in varying 

 proportions of two normal silicates, the trachytic and 

 pyroxenic. In the first of these (an acid silicate) the rela- 

 tion of the oxygen of the acid to that of the bases is as 

 3 :o'596, whilst in the latter (a basic silicate) the relation 

 is as3:l'998. This result, accompanied by an experi- 

 mental proof that the melting-point of different bodies is 

 differently raised under increase of pressure, led Bunsen to 

 assume that a crystalUsation of these two normal silicates 

 occurs in the earth's interior, and that all the eruptive 



rocks which reach the surface consist either of one or 

 other of these or of mixtures of the same. In the next 

 place they contain a full and successful research on the 

 so-called pseudo-volcanic phenomena of Iceland, in which 

 he investigates the formation of zeolites and other ci'ystal- 

 line minerals by the joint action of heat, acid gases, and 

 moisture on the volcanic rocks. He also examines the 

 composition of the fumerolle gases as well as those 

 issuing from the crater of Hecla, and explains the nature 

 of the changes effected by these gases on the surround- 

 ing rocks. Lastly, he investigates the far-famed Great 

 Geyser, and places the cause of the periodic eruption of 

 boiling water on its true physical basis. His accurate 

 observations on the spot, first as to the construction of 

 the geyser-tube, then as to its mode of formation, and 

 finally, his thermometric measurements of the tempera- 

 ture of the water-column taken a few moments before 

 the eruption and at different depths, disposed once for all 

 of what may be called the old tea-kettle theory, and 

 showed indisputably that in no part of the tube did the 

 water reach the temperature of ebullition under the pres- 

 sure of the superincumbent column, whilst the column is 

 quiescent, but that when the geyser column is elevated by 

 the rush of steam from the volcanic vents at the bottom, 

 the boiling-point of the water at each point of the column 

 thus raised is reached, and " the whole mass from the 

 middle downward suddenly bursts into ebullition, the 

 water above mixed with steam-clouds is projected into the 

 atmosphere, and we have the Geyser eruption in all its 

 grandeur. By its contact with the air the water is 

 cooled, falls back into the basin, partially refills the tube 

 in which it gradually rises, and finally fills the basin as 

 before. Detonations are heard at intervals, and risings 

 of the water in the basin. These are so many futile 

 attempts at an eruption, for not until the water in the 

 tube comes sufficiently near its boiling-point to make the 

 lifting of the column effective can we have a true 

 eruption " (Tyndall). 



To do justice to all the contributions with which Bunsen 

 has enriched our science would fiU several numbers of 

 Nature, and to many of them the writer must content 

 himself with a mere cursory reference. One of his 

 favourite and fruitful themes was the preparation by 

 electrolysis of the rarer or more difficultly procurable 

 metals. This is one of the purposes for which he 

 employed his battery. Metallic magnesium was one of 

 the first of his preparations of this kind, and in the 

 description of this preparation his fertility of resource is 

 clearly seen. Metallic magnesium in the molten state is 

 specifically lighter than the fused mixture of salts from 

 which it is obtained. Hence as soon as a globule of the 

 metal is formed, it rises to the surface, and there takes 

 fire and burns. To obviate this difficulty the carbon pole on 

 which the metal was formed was serrated, and the metal 

 on rising was caught, below the surface of the fused salt, 

 in one of a series of small pockets, and thus prevented from 

 burning. 



Then followed the reduction of chromium, aluminium, 

 and, in conjunction with the late Dr. Matthiessen, that 

 of the alkaline-earth metals, and more recently with 

 Hillebrand and Norton, of the metals of the cerium^ 

 group. These electrolytic researches are marked with 

 the thoroughness and completeness which is characteristic 



