160 fcioMK kecp:nt astronomical events. 



So highh' eccentric indeed was the planet's orbit that, although 

 upward of 90,000,000 miles distant at unfavorable oppositions, when 

 nearest the earth it nia}' come within about 15,000,000 miles, and 

 is on these occasions, so far as is known, our nearest celestial neigh- 

 bor after the moon. This peculiarit}^ caused the planet to beccjine an 

 object of great interest on account of its possible use in the more 

 accurate determination of the sun's distance from the earth, for an 

 object at 15,000,000 miles distance has a very appreciably different 

 position among the stars if viewed from opposite ends of the earth's 

 diameter — no less a parallax indeed than 100 seconds of arc. Con- 

 sequently its actual distance from the earth could probabl}^ be deter- 

 mined with ^•ery great accuracy-, and this distance when thus iixed 

 could be used indirectly to obtain a new estimate of the suiTs distance 

 from the earth, with an accuracy possibly exceeding that of earlier 

 methods. 



Search was inune'diately instituted by Prof. E. C. Pickering, the 

 director of Harvard College Observatory, through the contiiuious 

 photographic record of the stars which is kept up at that obser\atory, 

 for earlier positions of the planet, and such were soon found among 

 plates taken in 1898, 1894, and 1890. From these observations, which, 

 taken Avith those made in 1898, follow the planet through a consider- 

 able range of time, a ver}' accurate orl)it was computed." 



The or))its of Eros and the earth were found to be of such a form 

 that their next reasonably close approach would occur in Noxember, 

 1900, and while their distance at this time was indeed considerably 

 greater than their least possible distance of 15,000,000 miles, yet it 

 was determined to institute at that opposition a thorough parallax cam- 

 paign to be taken part in by all the observatories in the world fitted 

 with instruments suitable for this purpose, for it would be necessary 

 to wait upward of twenty yinirs for the minimum distance to occur. 

 Fully 50 obsei-vatories took part in this parallax campaign, continu- 

 ing observations from Oct()l)er through to al)Out the 1st of Fe])ruary. 

 These observations were in part photographic, in part visual, and 

 taken at stations as far apart astheCa})e of Oood Hope, South Africa, 

 and Helsing#ors, in Finland, and indeed it might almost ])e said that 

 there was no habitable quarter of the earth which was not represented 

 by observers. It is yet too early to say what will be the results, l)ut 

 it is hoped that they may lead to a very excellent determination of the 

 distance of the sun. 



"■As ail evidence of the valiu' uf tlie photographic records- of Harvard College 

 Observatory, it was recently remarked by Professor Pickering that "if, in the future, 

 any other ol)ject like Eros should be discovered, we have at this observatory the 

 means of tracing its path since 1890, during the time in which it was moderately 

 bright, with nearly as great accurat^y as if a series of observations bad been taken of 

 it with a meridian circle." 



