XX 



1854-56, partly according to methods devised by Angstrom. But the 

 fact that the observer had sometimes neglected to determine some 

 corrections which had to be applied to the observations, gave rise to 

 scruples in the mind of the calculator, in consequence of which the 

 work advanced so slowly that it was not finished and published until a 

 short time before his death in 1874. 



o 



The report of these labours of Angstrom forms part of the work pub- 

 lished by the Academy of Sciences of Stockholm, ' A Voyage Eound the 

 AVorld in the frigate ' Eugenie.' ' 



In the year 1852 the Eitig of Sweden granted new statutes to the Uni- 

 versities of the kingdom. Hitherto the duties of the assistant professors 

 had not been clearly defined ; but by these new statutes they were obliged 



o 



to give regular public instruction. During the next few years Angstrom 

 held the professorship of analytical mechanics. Subsequently when, in 

 consequence of enfeebled health, Professor Adolph Svanberg needed a 

 temporary holiday, Angstrom from time to time performed the duties of 

 the Professor of Physics ; and on the death of Adolph Svanberg he was 

 appointed Professor of Physics at Upsala, and was at last free to devote 

 all his energies to his favourite studies. 



Angstrom's most important papers are those on optics and on the 

 theory of heat. His first treatise, published on the occasion of his being 

 made Doctor of Philosophy, was on conic refraction, and that which he 

 pubKshed when candidate for the office of Professeur agrege bore the title 

 * De theoria lucis calorisque dissertatio.' Both treatises show his great 

 erudition in these subjects. He had an extraordinary fertility of ideas 

 and power of coordination. These intellectual qualities are conspicuous 

 in his suggestive dissertation, ' Essay on a Mathematical Theory of Heat.' 

 This paper was, however, never completed; and Angstrom considered that 

 it required to be completely recast. 



Closely connected with this last treatise was the note he published in 

 1842, on the occasion of the Meeting of the Scandinavian iS'aturalists at 

 Stockholm, and which appeared in Poggendorffs ' Annalen,' vol. viii., 

 " Einige Beobachtungen in Betreff der Warme und deren Theorie," as well 

 as his researches on the transmission of the heat of one metal to another 

 published, in 1860, in the Transactions of the Society of Sciences at 

 Upsala. 



To the theory of heat he contributed another important memoir, ' On 

 the Temperature of the Earth at different depths,' for which he had cal- 

 culated and worked out the observations on the temperature of the 

 Earth made by Eudbergat Upsala between the years 1837 and 1846. 



This work, and the ideas gained from his own previous experiments, 

 doubtless formed the basis of the new method of determining the con- 

 ducting-power of bodies for heat which he applied to solids in 1861, 

 and which he extended to fluids in 1862. This method has attracted 



