The binary character of the star, (1900 R.A. 22h 02m.0, Decl. +47° 45', Mag. 6.2,) was announced by the writer in 1919. At that time it was noticed that the H and K lines of calcium seemed to give nearly constant velocities and further observations have been made to investigate this and to determine the orbital elements.

The spectrum is classified as of type A in the Revised Harvard Photometry, H.A. Volume 50, but the later Draper Catalogue gives it as B3. The spectra taken here seem to show approximately the latter type or possibly B2, for the carbon line 4267 is quite strong. The lines are of rather poor quality and the calcium lines, usually so sharp and narrow in spectra where they do not shift with the other lines, are not very good. They are, however, better than the other lines. The velocities resulting from them are not included in the mean. In the table of 32 observations below they are listed under the heading "K line". In general the K line alone was measured, but sometimes when the shift of the neighbouring He line permitted, the H line could be measured also and in these cases the given velocity is the mean of the two lines.

The observations extend over an interval of 424 days, four plates being taken in 1918 and the remainder in 1919. The earlier plates were made use of only in determining the period. This was fixed at 2.1722 days and not included in a least squares solution made for the elements. It sometimes happens that a period determined in

this way needs to be modified slightly after the shape of the curve and its phase is rigidly determined and such is the case in the present instance. A period 2.1721 days will harmonize the early observations with the final curve better than 2.1722. The former period

1+ 4.1-11.0

0.3+ 6.0

+ 5.6 € 1.0

1-17.4 + 4.0 10.9 + 1.0 1 +20.0 +15.6

is taken as final. The observations were grouped into the following 14 normal places and preliminary elements selected upon which to base a least squares solution.

It seemed fruitless to attempt to solve for the eccentricity as the observations fitted a circular orbit very well. The element corresponding to periastron passage was taken as the instant when

the velocity curve crosses the y-axis while changing from a negative to a positive value. In this case the formulae for the least squares solution become

μ= 2π/P v = μt

Voy+K sin v

dVo-dysin vdK-Ku cos vdT

The final elements are given below

The results of the representation by the final elements as well as those for the preliminary will be found in the table of normal places. The po for the preliminary elements is 585 and for the final 509. The residuals computed from the observation equations agree very closely with the final ephemeris so that there can be no doubt of the sufficiency of the solution. The residuals for the