554 



NATURE 



[July i, 1920 



lenger was making for the Raine Island passage, 

 observations were taken at 5 a.m. of Aldebaran, 

 Sirius, and Canopus, and the latitude was assumed 

 to be 1 1° 40' S. or 1 1° 50' S. Using these latitudes, 

 the position of the Sumner lines was found to be 

 as shown in Fig, i, and the position of the vessel 

 to be 11° 44' S., 145° 4' E. 



(2) On June 13, 1874, observations were taken 

 at 6 a.m. (to fix the position of a deep-sea sound- 

 ing) of )8 Orionis, Canopus, and Saturn, the lati- 

 tude being assumed as 34° 12' S., the resulting 

 longitude by )8 Orionis being 151° 56' E., and its 

 azimuth S. 86° 26' E., the Sumner line therefore 

 running N. 3° 34' E. and S. 3° 34' W. The longi- 

 tude by Canopus was 151° 50' 45" E., and its 

 azimuth S. 39° 18' E.,' its Sumner line running 

 N. 50° 42' 'e., S. 50° 42' W. ; the longitude 

 by Saturn was 151° 54' 15'' E., and its azimuth 

 N. 73° W., and the Sumner line by it running 

 N. 17° E., S. 17° W. These lines are shown in 



Fig. 2, and the position of the sounding was 

 lat. 34° 8' S., long. 151° 56' E. 



But the Sumner line has another advantage. 

 When only one heavenly body is visible, and, 

 therefore, the exact position of the observer 

 cannot be obtained, if with an assumed lati- 

 tude the longitude and azimuth be calculated, and 

 the resulting Sumner line be plotted on the chart, 

 if this line runs in the direction of the port, or 

 point of land, towards which the ship is sailing, 

 by steering along the Sumner line the vessel will 

 reach her destination. For instance, if when 

 sailing towards the English Channel an observa- 

 tion of the sun be obtained in the forenoon, when 

 its azimuth, or true bearing, is somewhere 

 between south and east, the Sumner line will be 

 between east and north ; and if this line runs 

 towards the Lizard or some other known point, by 

 steering along this Sumner line a good landfall 

 may be obtained. 



Obituary. 



Dr. F. a. Tarleton. 



FRANCIS ALEXANDER TARLETON, who 

 died on June 20, was born in Co. Monaghan 

 in 1841. He was the youngest son of the late 

 Rev. J. R. Tarleton, of the Established Church in 

 Ireland, and received his earlier education from his 

 father. At the age of sixteen he entered Trinity 

 College, Dublin. He was in the same year as the 

 late Sir Robert Ball, whom he defeated at the 

 moderatorship examination in mathematics in 

 1861, taking also a junior moderatorship in logic 

 and ethics. Elected to fellowship in 1866, and 

 called to the Bar in 1868, he was for a time assist- 

 ant to the professor of applied chemistry, and pro- 

 fessor of natural philosophy from 1890 to 1901, 

 when he was co-opted a senior fellow. From that 

 time until a few days before his death he sat as 

 an efficient member of the board of Trinity College. 

 Dr. Tarleton held several college offices, including 

 those of senior bursar, senior lecturer, and senior 

 dean, the last being a sinecure — for its statutory 

 duties have long since lapsed. As senior bursar he 

 showed his qualities as a first-class financier. He 

 was at one time president of the Royal Irish 

 Academy, and a member of the Board of Irish 

 Intermediate Education. 



As professor of natural philosophy, Dr. Tarleton 

 followed the traditions of his distinguished pre- 

 decessors, Williamson, Townsend, and Jellett, in 

 treating the subject from a strictly mathematical 

 point of view. Although he had a considerable 

 practical acquaintance with experimental science, 

 he flatly ignored the judicial aphorisms of Francis 

 Bacon, and, instead of treating mathematics as 

 the handmaid of physics, he rather inverted the 

 order, and almost succeeded in reducing hydro- 

 dynamics, elasticity, magnetism, and electricity to 

 branches of pure mathematics. 



The writer attended Dr. Tarleton 's moderator- 

 NO. 2644, VOL. 105] 



ship and fellowship lectures about twenty years 

 ago in hydrodynamics, elasticity, and the electro- 

 magnetic theory of light, and was struck with 

 wonder at his extraordinary memory and 

 accuracy. For two and a half hours he 

 would write down long and intricate calcula- 

 tions without the aid of any notes. Some- 

 times a student at the end of an hour would 

 ask to be allowed to leave in order to attend a 

 lecture in experimental science or history or other 

 subject, and Dr. Tarleton would say with a snarl 

 and a grimace (covering a heart full of humour 

 and humanism) : " Waal, if you prefer that 

 abominable subject to mathematics, you are wel- 

 come to leave, and we're glad to get rid of you." 



The last time the writer spoke to him. Dr. 

 Tarleton expressed his intense dislike of Einstein's 

 theory of relativity. He held that the Newtonian 

 and Kantian conceptions of space and time are 

 good enough to explain all possible phenomena, 

 if sufficient mathematical ingenuity is shown, and 

 he placed relativism in the same category as 

 Bolshevism. 



Dr. Tarleton wrote the following papers :— "On 

 the Solid of Revolution having a Given Volume 

 which experiences the Least Resistance in Passing 

 Through a Mediuln," "Chemical Equilibrium," 

 "Deductions from MacCullagh's Lectures en 

 Rotation," "The Foundations of the Science of 

 Number," "Notes on Crystallography," "Geo- 

 metrical Proofs of Some Properties of Conies," 

 "The Harmonic Determinant," "Laplace's Co- 

 efficients," and "A Problem in Vortex Motion." 

 His two books " Dynamics " (written in conjunc- 

 tion with Williamson) and " An Introduction to the 

 Mathematical Theory of Attractions " . are first- 

 class text-books of their kind. The latter contains 

 a chapter on Maxwell's electro-magnetic theory 

 of light. R. A. P. Rogers. 



