23® Dr. Herschel on the Quantity 
projectile motions, and to be subject to the attraction of far 
distant centres. 
Determination of the Quantity of the Solar Motion. 
If I am not mistaken, it will now be allowed that no ob- 
jection can arise against any solar velocity we may fix upon, 
for want of a cause that may be assigned to act upon the sun, 
and many stars, so as to account for their motions, and similar 
tendency towards a certain part of the heavens ; we may 
consequently proceed in examining whether the quantity that 
has been assumed for calculating the contents of the Xlth 
Table, will sufficiently come up to the conditions we have 
adopted for directing our determination. 
In Fig. 6 we have the velocities of the 36 stars delineated, 
and by examining the last column of the Table from which 
they are taken, we find that the parallactic effects arising 
from the proposed solar motion require the velocity of 18 
stars to exceed that of the sun, and exactly the same number 
to be inferior to it ; so far then the rank which has been as- 
signed to the solar motion is a perfect medium among the 
sidereal velocities. 
If we examine in the next place how this motion will agree 
with a mean rate deduced from the velocities in the above 
mentioned column, we find a 36th part of their sum to be 
1196550. A solar motion, therefore, which agrees with this 
mean rate will differ from one assigned by the middle rank 
no more than o", 079558 ; and, on account of the smallness 
of this quantity, the calculations required to lessen it, by some 
little increase of the solar motion, might well be dispensed 
with; but if we were desirous of greater precision, the 
