208 Transactions of the Boyal Society of South Africa. 
way as he went ; he seemed to plunge into the very centre of the region 
of investigation. 
His outward actions were an index of tliis quahty of mind. Those of 
us who knew him well will remember his quick, swift movements, his 
rapid speech — words tumbling over one another, his habit of switching 
the conversation suddenly from one topic to another, his intense absorp- 
tion in any matter that interested him, his study table piled high and 
running over with books, charts, tables, papers, and parts of instruments. 
These were only some of the countless ways in which his intensity of 
mind, his impatient patience, revealed itself. 
Gill's work at the Cape embraces four outstanding investigations, and 
three or four lesser activities. 
The first four are : a series of determinations of stellar parallax ; an 
exhaustive determination of the sun's parallax ; a complete geodetic 
survey of South Africa ; a photographic durchmusterung of southern stars 
brighter than the tenth magnitude. 
Less laborious, though perhaps not much less important investigations, 
are the mass and parallax of the moon ; the mass of Jupiter ; the position 
of close circumpolar stars ; an inquiry into the influence of brightness 
upon transits. 
Besides these distinctive operations there was the constant supervision 
of the routine service of a large observatory — time determinations ; 
astrophysical work on the spectra of stars ; latitude and longitude 
determinations ; variation of latitude ; the constant of aberration ; 
fluctuations in level due to tidal pressure or seasonal changes ; regular 
meteorological work. 
Of the four outstanding investigations, the triangulation of South 
Africa and the determination of the length of the longest possible arc 
of meridian, might be considered as one of the most necessary inquiries 
to which a public observatory could devote itself. It was not only a work 
of national importance, but it was also one of great scientific value, as it 
afforded data for a determination of the earth's figure. 
It was an investigation which very early in his South African career 
interested Gill, and to which he devoted some of the best years of his life, 
undertaking long journeys almost into the very heart of Africa, spending 
hours and much energy — no small part of it in curbing impatient speech 
— in interviewing ministers and officers of state in order to secure the 
necessary funds and surveyors to carry on the work, and finally wading 
through interminable figures and drawmgs so that there might be co- 
ordination and unity in the vast undertaking. 
The work was set in motion in 1883, and when Gill left the Cape in 
1906 he had the satisfaction of knowing that every part of South Africa 
was triangulated with a completeness and an accuracy unsurpassed in 
