Scope and Contents Correspondence concerning improved instruments, new techniques and inventions, and a proposed planetarium and cometarium. The new inventions include improved sextants and sea horizons; a micrometer; a paper on finding Greenwich Time, complete with a drawing; achromatic eyepieces; an improved quadrant; drawings of eye pieces; a heliotrope; and an illuminating process for telescopes. The correspondents include Sir B. Donkin, Sir C. Wood, Sir H.G. Ward, Sir W. Denison, J. Challis, C.B....