These errors in the needle that guides the ship, so dangerous in their results, at last attracted official attention in England. Inquiries were extended in various directions, and it was found that “in some ships the deviation was small; in others it was large enough to cause the loss of a ship, even during a short run; whilst in others, again, from the position of some iron stancheon, bolt or bar, or stand of arms, the error might be changed in the opposite direction; so that the deviation in one vessel was not a guide to its amount or direction in another; and that there was no other remedy but ascertaining the fact by direct experiment in each ship.” These facts were recognised by a committee of English officers, appointed to investigate the matter, one of whom was the Captain Johnson whom we have already quoted, and of whose subsequent labours we shall have further presently to speak. With these words of explanatory preface, let us set out on a visit to the establishment where the dangers of those afloat are sought to be lessened by scientific investigations on shore. About two miles and a half eastwards from the Greenwich Observatory, in the picturesque parish of Charlton, and on the extreme corner of the high land that runs from Blackheath, till it juts out close upon the banks of the Thames—stands the building we are in search of. Those who may try to discover it will probably find some little difficulty in the task, for the place is unpretending in outward aspect, and is little known in the neighbourhood; has never before been publicly described—except, perhaps, in those unread publications called Blue Books, and in the technical volume of the naval officer who has charge of this sanctum of science. It is called the Compass Observatory; and its locality may probably be more completely indicated by saying that it is not very distant from, though on a far higher level than that corner of the Woolwich Dockyard whence the great chimney soars up like a rival monument to that on Fish Street Hill, and where the engine that sets the Dockyard Machines in motion hums like a bee of forty-horse power. When the place is reached, those who expect to see “a public building,” will be disappointed; those who like to find that Science may abide in small and humble places, will be pleased. A long strip of newly-reclaimed land, a detached brick house, and in its rear, an octagonal wooden structure of little greater outward pretensions than a citizen’s “summer house,” make up the whole establishment.