SCIENTIFIC SUMMARY. 
307 
change of place, amounting to 2 //, 0, hut the measures of direction are in 
themselves much easier, and more certain than those of distance. 
u It is well known that Professor Auwers, as soon as he had received my 
observations of last year, repeated his investigations into the variable proper 
motion of Procy on,. availing himself also of the observations of this star 
which have been made since 1862. From this he concluded that it was 
doubtful whether the object observed by me was really the sole body 
disturbing the proper motion of Procyon, but that the doubt would be 
removed if it appeared this spring that the position-angle had undergone an 
increase of from 9° to 10°. And this increase has really shown itself above 
in the most remarkable manner. I consider it, therefore, to be decisively 
established that the object I have observed is actually the companion whose 
existence has been theoretically proved by the calculations of Auwers, 
and hope that the astronomical world will rejoice with me in the triumph 
thus obtained for the labours of my honoured friend, and through them for 
our common science. In order to remove any exception that might be taken 
that the wished-for result had in any degree been itself the cause of the 
recognition, and affected the measurement of the place of so difficult an 
object, I will just remark that I had not looked again at the paper of 
Auwers in question since its first receipt last summer, and had totally for- 
gotten the data of its criterion, and the mutual relation of the two stars. 
I did not again take it up until after I had succeeded in making the first 
observation, and the results of that paper were even less present to the 
mind of my assistant, Herr Lindemann, whose younger eye appears gene- 
rally to have seen the companion even better than mine.” 
Determining the Solar Parallax by Observations of Juno at Opposition . — 
Lord Lindsay and Mr. Gill, in a recent number of the “ Monthly Notices of 
the Astronomical Society,” describes their plans for observing Juno in order 
to determine the sun’s distance. “ The method recommends itself,” they re- 
mark, “ not by a favourable factor of parallax such as is afforded by a transit 
of Venus or a favourable opposition of Mars, but by the extreme precision 
with which a minute point of light can be bisected as compared with that 
with which a web can be brought into contact with a disc. We are not 
aware that any results have been published of the application of the method, 
though there is no doubt that it is capable of great accuracy. It has ap- 
peared to us that if we select suitable stars, and observe the parallactic dis- 
placement of a minor planet relative to these stars by the Earth’s rotation, 
we have a method of determining the solar parallax, which is free from the 
difficulties and disappointments attending observations in which co-opera- 
tion is necessary, and where the most complete arrangements and perfect 
observation may be upset by unfavourable weather at the opposite station. 
u The accuracy of the proposed method will depend — 
“ 1. On the amount of displacement that can be measured. 
u 2. The accuracy with which the measures can be made. 
a 3. The number of nights on which the measures can be repeated, 
which will partly depend on the nights on which suitably 
situated stars of comparison can be found. 
11 The planet Juno at the opposition of 1874 appears to be very favour- 
ably situated for a trial of this method. Mauritius (the station where we 
x 2 
