226 MEMORIES OF MY LIFE 



Magnetic Observatory of the world. It held an 

 almost equally strong position in respect to the delicate 

 pendulum apparatus by which the force of gravity is 

 measured at different places on the globe, and again with 

 regard to standard thermometers and meteorological 

 instruments generally. Its Managers were eager to 

 extend its operations to any kind of self-paying 

 scientific experiment. Any person desirous of having 

 a new invention tested could get it well done there 

 at a cost that just repaid the trouble, subject, of 

 course, to the permission of the Managing Committee 

 and to the leisure of the staff. 



One of the first things that I busied myself about, 

 when I joined it, was to establish means for standard- 

 ising sextants and other angular instruments. The 

 cheaper kinds of these were unnecessarily bad, and 

 many of the more costly were by no means so good 

 as they should be for their price. I thought at first 

 of utilising heliostats to give sharp points of reference 

 by adjusting minute mirrors at distant points, flashing 

 the sun on to them from larger mirrors at the Obser- 

 vatory, and using the return flashes as the points of 

 reference. One of these small mirrors was fixed to 

 the south obelisk, within a cage which may still be 

 there. This arrangement was so far successful that 

 beautiful stars of light were produced in response to 

 flashes from the Observatory, but the uncertainty of 

 sunshine in our climate showed the method to be of 

 little practical value. Then Messrs. Cooke of York, 

 who were anions: the foremost makers of laree tele- 

 scopes, devised an arrangement with collimators and 

 artificial light. They made one for Kew, which is 

 contained within a small dark room, and has acted 



