xl Proceedings of tJie South African PJiilosojMcal Society. 



The tablet was designed, as a labour of love, by Messrs. Herbert 

 Baker and Masey, architects, of Cape Town, and it is now before 

 you to-day, preparatory to being placed on a site the nearest prac- 

 ticable to the spot where Lacaille lived and worked. 



It bears, as astronomical symbols, the stars of the Southern Cross 

 and Lacaille's quadrant ; the geometrical figures represent the plan 

 of Lacaille's measurement of an arc of meridian at the Cape, another 

 of his labours to w^hich further reference will presently be made. 



The reasons why Lacaille selected the Cape of Good Hope as the 

 scene of his labours are not far to seek. A glance at the map of 

 the world and some slight knowledge of the history of civilisation 

 will show that in 1752 the Cape of Good Hope was perhaps the only 

 spot situated in a considerable Southern Latitude which an unpro- 

 tected astronomer could visit in safety, and where the necessary 

 aid of trained artizans to erect his Observatory could be 

 obtained. At the Cape these advantages had existed for a 

 century, and besides being the most southerly point conveniently 

 available, it is situated nearly in the same meridian as Central 

 Europe, so that almost simultaneous meridian observations of the 

 Moon and Planets could be made in both hemispheres for the purpose 

 of determining their parallax, or the same phenomena of Jupiter's 

 satellites could be noted in both hemispheres for the purpose of 

 determining the longitude of the Cape. 



In these days the longitude of the Cape was very imperfectly 

 known. Nowadays there are few points on the habitable parts of 

 the globe whose longitude is not known within three or four miles, 

 and all important points within a fraction of a mile ; but in 

 those days there" was an uncertainty, as to the longitude of the 

 Cape, of many miles. To secure a fresh and well-determined depar- 

 ture from a point which would be sighted or touched by most vessels 

 bound to or from the East Indies was a matter of practical impor- 

 tance so well understood that it furnished the most powerful 

 argument for smoothing Lacaille's path, and was accepted by 

 Governor Tulbagh as a sound reason for giving Lacaille a hearty 

 welcome, building an Observatory for him, and affording him 

 every aid. 



The Cape may thus be regarded as the birthplace of exact 

 astronomy in the Southern Hemisphere. 



Erom the days of Lacaille practically nothing was done in the way 

 of Southern Astronomy for seventy years, until the year 1821, when 

 Sir Thomas Makdougall Brisbane, having been appointed Governor 

 of the Colony of New South Wales, and being himself an ardent 

 iimateur of the science, resolved to establish an Observatory at his own 



