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124 and how, when the difficulty of colour was got over, large lenses also began to be made. Meantime the tube had to grow to keep pace with the growth of the object end, and the old difficulties of unwieldiness had to be faced afresh;

and so we came back to the tube and learnt about the coelostat, and ultimately about Professor Hale's great 150-foot tower. But all this time nothing had been said of the poor eye end, which seems to have been left quite out in the cold: and indeed its history did not begin until later, but once begun, it has been far