ever, that the possibilities of the new method were much greater than had been indicated by the work so far accomplished. It seemed certain that our knowledge of the finer details of the calcium clouds would be greatly increased if provision could be made for photographing a much larger solar imago with a spectroheliograph of improved design. And
it was furthermore evident that other applications of the instrument, involving the use of different spectral lines, and the employment of principles which had not entered in the Kenwood work, might reasonably be hoped for.
The construction of the great forty-inch telescope of the Yerkes