of ash-tree, and used no other.  The chiefest difficulty was to get the clay for the pots to melt the materials in; this they had out of the north.”—­Chap.  XXI., Sect.  VIII.  “Of the Glass made in Ireland.”

Birr Castle itself is a noble mansion with reminiscences from the time of Cromwell.  It is surrounded by a moat and a drawbridge of modern construction, and from its windows beautiful views can be had over the varied features of the park.  But while the visitors to Parsonstown will look with great interest on this residence of an Irish landlord, whose delight it was to dwell in his own country, and among his own people, yet the feature which they have specially come to observe is not to be found in the castle itself.  On an extensive lawn, sweeping down from the moat towards the lake, stand two noble masonry walls.  They are turreted and clad with ivy, and considerably loftier than any ordinary house.  As the visitor approaches, he will see between those walls what may at first sight appear to him to be the funnel of a steamer lying down horizontally.  On closer approach he will find that it is an immense wooden tube, sixty feet long, and upwards of six feet in diameter.  It is in fact large enough to admit of a tall man entering into it and walking erect right through from one end to the other.  This is indeed the most gigantic instrument which has ever been constructed for the purpose of exploring the heavens.  Closely adjoining the walls between which the great tube swings, is a little building called “The Observatory.”  In this the smaller instruments are contained, and there are kept the books which are necessary for reference.  The observatory also offers shelter to the observers, and provides the bright fire and the cup of warm tea, which are so acceptable in the occasional intervals of a night’s observation passed on the top of the walls with no canopy but the winter sky.

Almost the first point which would strike the visitor to Lord Rosse’s telescope is that the instrument at which he is looking is not only enormously greater than anything of the kind that he has ever seen before, but also that it is something of a totally different nature.  In an ordinary telescope he is accustomed to find a tube with lenses of glass at either end, while the large telescopes that we see in our observatories are also in general constructed on the same principle.  At one end there is the object-glass, and at the other end the eye-piece, and of course it is obvious that with an instrument of this construction it is to the lower end of the tube that the eye of the observer must be placed when the telescope is pointed to the skies.  But in Lord Rosse’s telescope you would look in vain for these glasses, and it is not at the lower end of the instrument that you are to take your station when you are going to make your observations.  The astronomer at Parsonstown has rather to avail himself of the ingenious system of