SECTION III. 1883. 2521 Trans. Roy. Soc. CANADA. 
On a Mechanical Means of making a Sidereal Clock Show Mean Time. 
By N. F. Duputs. 
(Read May 26, 1883.) 
The object of the present paper is the solution of the mechanical problem, to find a train 
in which the angular velocity of the first driver to that of the last follower may be aecu- 
rately as the length of a mean solar day to that of a sidereal day. This is not a new pro- 
blem but, as far as I am aware, the solution here presented is not only new but also 
simpler and more accurate than any hitherto presented. 
A solution due to Francœur and quoted by Willis, contains the numbers 
8 X 137 
7 X 157 
which gives an error in the final result of about 211 seconds a year, so that such a clock, 
if keeping correct sidereal time, would get about one minute out in mean time in three 
years. 
Another solution is given in “ Willis Mechanism,” article 423, but the solution is com- 
plieated and is by no means accurate. Still another solution is given by Margett, which, 
however, offers no peculiarities of excellence. 
In his work on “ Clocks, Watches and Bells,” Sir Edmund Beckett gives the solution 
32 
43 — 331 
247 
without stating to whom it is due. 
But this is scarcely a practical solution inasmuch as the numbers 247 and 331 are 
beyond those usually available in clock-work. Besides the solution is not nearly as accurate 
as stated in the work referred to. 
From the nature of the solution given in this paper the principal motion is a differen- 
tial one, and, all the motions being thus rendered slow, the amount of friction and of extra 
power required is reduced to a minimum. 
As to the utility of the arrangement by which a clock keeping sidereal time may be 
made to show also mean time or vice versa, Sir Edmund Beckett says, in regard to the solu- 
tion given by him, that it is “ more ingenious than useful.” While I cannot question the 
ingenuity displayed in many of our mechanical inventions, I particularly dissent from the 
conclusion implied in the latter part of his statement, viz., that it isnot useful. This, how- 
ever, is not a subject for discussion in the present article, and I have only to say that, hav- 
ing a clock so constructed, I have at times found it particularly useful and convenient. The 
clock to which I refer is a sidereal one, with the attachment hereafter described and an 
additional dial, showing mean time. 
