THORX'ALD XICOLAI THIELE. 



Bv F. A. BELLAMY. Hon. M.\.. F.K.A.S. 



Thiele was born on December 24th. 1838. in 

 Copenhagen, and was a scion of a respected and 

 well-educated famih'. He shewed, very early in life. 



distinct talents for the 

 mathematical profession, 

 and kept himself abreast 

 of the mathematical pro- 

 ,;;ress of his time. His 

 tutor in Astronomy was 

 d" Arrest, and he obtained 

 his Master's degree in 

 1860. about which time he 

 accom[)anied d'Arrest to 

 .Spain, to observe the total 

 eclipse of the sun. In 

 1866 he ga\e his inaugural 

 dissertation, and discussed 

 the relative motions of the 

 double star y \'irginis : 

 Danish, and hlled one 



Thorvald Nicolai Thiek-. 



this was published 

 hundred pages. 



In 1870 he turned his attention to another depart- 

 ment of applied mathematics which interested him. the 

 problems of life assurance. His work in this subject 

 was first directed to the difficult problem of the 

 adjustment or settlement of the mortality tables : into 

 this Thiele penetrated ver\- deepK-, and was doubtless 

 one of the earliest explorers in this subject. 



.\s a recognition of this scientific work he had the 

 honour of being elected a foreign member of the 

 Institute of Actuaries in London : while in Denmark 

 he had great influence, and held a position of great 

 importance as Chairman of "Foreningen af danske 

 Aktuarer," and was Director of the Life Assurance 

 Societv " Hafnia," from 1872. 



Of his other works mention must be made of the 

 "Theory of Obser\'ations,"' which was printed in 

 English at Copenhagen, and published in London in 

 1903; and of "Interpolations rechnung." Through 

 the impulse which he had given to the subject of 

 the numerical researches concerning some periodic 

 solutions of a special case of the problem of three 

 bodies, Thiele rendered an ackno\\ledged service to 

 Astronomy, both of great and general value. His 

 love for double-star astronomy was continued 

 throughout his life ; and attention ma\- be dra^\■n to 

 Otto Struve"s criticism on the determination of the 

 systematic errors of double-star observations in the 

 Vierteljahrschrift der Astrniinniisclic Gcsclhclmft 

 (Leipsic) for 1880. 



Besides these publications he contributed many 

 notes, articles, and memoirs to the current scientific 

 journals of his day. Most of his astronomical contri- 

 butions were sent to the Asfroiioniische Xacliriclitcji 



and commenced as far back as 1859 at the age of 

 twentv. when he wrote upon the double stars S Librae, 

 Castor, and upon Sun-spots: in 1860 a note on the 

 Eclipse of the Sun ; and in 1861 a paper on the 

 Latitude of the Observatory at Copenhagen appeared. 



From that time we find he contributed to science 

 papers of more or less importance in several branches 

 of Astronom\'. and mention ma\' be made of those 

 upon Double-star Orbits — where he proposed new- 

 methods : a Geometrical Problem in Theoretical 

 Astronom\- : Longitude between Lund and Copen- 

 hagen (with Duner) : Orbits and Ephernerides of 

 Minor Planets ; Ouasi Errors of Least Square Method: 

 Ikihnberegning for Planetes \id en modification af de 

 Kepplerske lore: On some Interpolation Formulae 

 for Double-Stars (Copcniiciis II. p. 25-41) — this 

 gives six methods of using the observations, and 

 tables are furnished to assist the calculations ; also he 

 wrote obituarv notices of Schjellerup and Svedstrup. 

 His important and concise paper on the motion of the 

 Double-Star Castor was carefulh- written, in French, 

 and is evidence of a w ide grasp of that particular 

 subject and extensi\e reading: it formed one of the 

 communications made in 1879, when the four 

 hundredth anniversarv of the formation of the 

 L'niversit\' at Copenhagen b\- Christian I, in 1459. 

 was celebrated. 



Thiele was an eminenth' gifted man. The 

 extent of his reading and the range of subjects \\ hich 

 interested him was in a great degree exhibited in a 

 marked manner when lecturing to his audiences; 

 but, though Thiele probably excited some enthusiasm 

 among his scholars, he had not in a high degree that 

 influence in university teaching which one might 

 ha\'e expected from a man of his talents. He was 

 of a neat and engaging appearance, and, although 

 he was of a reserved or retiring disposition, it was 

 not eas\' to consult or approach him \\ ith questions, 

 but he was alwavs a true friend to those who 

 succeeded in doing so. He was no mean linguist, 

 and as evidence of his powers the papers just 

 referred to were written in one or other of these 

 languages — Latin. Danish. German. French or 

 English. 



Thiele was appointed a Professor in the University 

 of Cojienhagen and Director of the Observator}-, 

 which was re-built and re-organised in the early 

 jieriod of his predecessor's reign (d'Arrest), in 

 October of 1875 ; he retired as Emeritus Professor a 

 few vears ago and was succeeded b}- Stromgen. 



The writer is indebted to Herr C. Burran's 



biographical notice for some of the information 



given, and to the Asfroiioniische GeseUschaft 



(Leipsicj for permission to reproduce the portrait. 



504 



