ve es rae a 
Fune 23, 1870| 
NATIURE 
145 
world, it was in a new science. He was created Professor 
of Natural Philosophy in 1834, and no research of his 
was published during the following three years, evidently 
spent in qualifying himself for his new position. Re- 
searches on steel magnets and on the boiling of liquids 
reopened the series of his discoveries in 1836; still he 
had not escaped the sway that chemistry exercised over 
his mind. Papers on the composition of a fossil resin, 
ozokerite, on the gases contained in blood, and on the 
combination of ethylene with sulphuric anhydride (car- 
byl-sulphate) were published in 1837 and 1838, and even 
later researches on the formation of tar from ethylene, 
and on the allotropic modifications of sulphur (1856),* 
show how much chemistry lost when natural philosophy 
took possession of Magnus’s talents and energies. Later 
his modesty urged him to disclaim the honours so 
largely gained through his chemical researches. When 
after the opening of a university laboratory by Prof. 
A. W. Hofmann, the expanding scientific interest led to 
the formation of the German Chemical Society (in 1867), 
Magnus could only be prevailed upon with difficulty to 
become one of its vice-presidents, and although he worked 
on the committee with zeal, offering assistance and advice 
wherever it was needed, and publishing a paper on the 
diathermanity of chloride of potassium in the Reports of 
the Society, he pretended that he had lost all claims to be 
regarded as a chemist. 
We have to revert, therefore, to the second side of his 
scientific work, his researches in natural philosophy. A 
determination of the expansion of air, instituted at the 
same time (1842) and in ananalogous manner, by Magnus 
in Berlin, and by Regnault in Paris, and yielding all but 
absolutely the same numerical results, proved the exact- 
ness of both physicists. The most admirable conformity 
distinguished likewise researches on the tension of va- 
pours, which both savazts executed independently of each 
other in 1844, by entirely different methods. Relating 
chiefly to the tension of steam, the results thus obtained 
are as important for practical as for scientific purposes. 
Researches on the tension of vapours given off by mix- 
tures of different liquids, and a comparison of the mercury 
thermometer and the air thermometer, preparatory to the 
great investigations just referred to, were published at the 
same time. 
In 1855 Magnus investigated the form which jets of 
water assume when issuing from apertures of different 
shapes, and thereby opened to experimental study the 
surface-tension of liquids. His inquiry extended to the 
manner in which the motion of the aperture influences the 
form of the jet. Two years later he published detailed 
investigations on electrolysis. The discussion of this 
complicated question he founded on the theory of chemical 
substitutions, The temperature of vapours and the con- 
ducting power of gases formed the subject of his researches 
up to 1861. Until then gases had been considered as non- 
conductors. He proved that hydrogen conducts heat in 
the same way as do solid bodies, and thereby established a 
new and striking analogy between this element and metals. 
During the last years of his life the radiation of heat 
formed the chief object of his researches. A paper on 
the polarisation of the dark rays of heat, the discovery 
of the diathermanous nature of native chloride of 
potassium, and lastly a full research on the emission, 
absorption, and reflexion of heat radiated at low tempera- 
tures, were the results of this protracted and fertile investi- 
gation. He showed that heat from different sources is 
refracted under different angles, and absorbed in different 
proportions by the chlorides of sodium and of potassium, 
by fluor-spar and other substances. He thus proved, 
* The latter investigation contained an error which was afterwards cor- 
rected by its author, and originated a new discovery. Magnus found that sul- 
phur acquired a deep red or black colour when fused with minute quantities 
of various organic substances. This change was at first ascribed by him 
to an allotropic modification of the element. 
that, if our eyes were able to distinguish different rays of 
heat, we should see the different substances giowing in 
the most varied colours at ordinary temperatures, just as 
we see them emit different rays of light when exposed to 
heat and observed with the spectroscope. 
The receptacle of all his researches is the “ Annals of 
Chemistry and Natural Philosophy” (Azalen der Chemie 
und Physik), published by his friend Poggendorff. He 
formed a fine collection of scientific apparatus, afterwards 
bought by the University and put under his control. As 
a lecturer, Magnus was a pattern of clearness. He loved 
teaching, and his diction, though plain, showed the high 
culture of his mind. While in his lectures he aimed at 
being comprehensible to the large number of students who 
wished to learn the rudiments of science, he instituted 
special classes for those who longed to enter into a deeper 
study of natural philosophy. Graduates and under- 
graduates assembled around him once a week, to enjoy 
what he called physical conversations. Here students 
in turn reported on investigations recently published, the 
master criticising the report and opening a discussion on 
those points which appeared to deserve a fuller explana- 
tion. Some favoured pupils were instructed in the 
methods of physical researches in his private laboratory, 
the master allotting subjects to them, urging them 
above all to exactness, and warning them against drawing 
hasty conclusions from their experiments. Many profes- 
sors of natural philosophy, who have since obtained fame 
or reputation, have been educated in these classes. From 
a long list of names we will but mention those of Tyndall, 
Clausius, Wiedemann, Heusser, Quincke, Palzow, Villari, 
and Kundt. The laboratory joined his apartment, and 
he was thus enabled to watch from his sick-bed the 
investigations that occupied his thoughts. Magnus’s 
health had been impaired for many months. He was 
suffering when he visited the last mecting of the British 
Association at Exeter. He was ill when he presided at 
the banquet given to Professor Hofmann on the 8th of 
January. Still he continued his work up to the beginning 
of February, when weakness and excruciating pain forced 
him to give up his lectures. He foresaw his death, and 
made the most minute arrangements, order being one 
of the characteristic properties of his mind. “I have 
written to you to ask for your advice,’ he addressed 
his physician, “but I foresee that my case will give you 
but little satisfaction.” 
Magnus married the daughter of M. Humblot, a well- 
known publisher. His wife, as well as two daughters and 
one son, survive him. The circle that assembled at his 
house was very large, and included the leading members 
of every profession, members of the university, merchants, 
statesmen, and artists. But he was equally accessible to 
every unknown youth who wanted his advice and assist- 
ance. Ever ready to help, he bestowed his aid, as if he 
received, not as if he conferred, a favour. Gentle- 
mannered, conciliatory, and persuasive, he was the 
mediating element of every society. Nothing can show 
better the kindness of his disposition than the love which, 
not his family or his pupils only, but even his domestics, 
bore for him. A faithful laboratory servant, who took 
care of his instruments and also nursed him through his 
last illness, bears witness that he could not endure to see 
unhappiness or unpleasantness around him. ‘“ Why,” 
he would ask sometimes, “will you make life difficult to 
yourselves? Is it not sufficient your Master should make 
it difficult for you?” 
His death is therefore felt, not only as a severe loss to 
science, but as a personal pain, by all who had the good 
fortune of approaching him. Numerous were those who, 
on the 8th of April, thronged the room where his coffin 
stood, hidden under palms and flowers. Some parting 
words were spoken by Dr. Miillensiefen, Professor of 
Divinity, and a song of Mendelssohn, sad, yet cheering, 
ascended from his grave, A. OPPENHEIM 
