The weather here is still vexatious: but not absolutely repulsive. Yesterday morning Lord Rosse arranged a new method of suspending the great mirror, so as to take its edgewise pressure in a manner that allowed the springy supports of its flat back to act. This employed his workmen all day, so that the proposed finish of polishing the new mirror could not go on. I took one Camera Lucida sketch of the instrument in the morning, dodging the heavy showers as well as I could; then, as the afternoon was extremely fine, I took another, with my head almost roasted by the sun. This last view is extremely pretty and characteristic, embracing parts of the mounting not shewn well in the others, and also shewing the Castle, the Observatory, and the 3-feet telescope. The night promised exceedingly well: but when we got actually to the telescope it began to cloud and at length became hopeless. However I saw that the fault which I had remarked on the two preceding nights was gone. There is now a slight exhibition of another fault to a much smaller extent. We shall probably be looking at the telescope to-day in reference to it. THE CASTLE, PARSONSTOWN, _1848, Sept. 1_. Yesterday we made some alterations in the mounting of the great mirror. We found that sundry levers were loose which ought to be firm, and we conjectured with great probability the cause of this, for correction of which a change in other parts was necessary. The mirror was then found to preserve its position much more fixedly than before.... At night, upon trying the telescope, we found it very faulty for stars near the zenith, where it had been free from fault before. The screws which we had driven hard were then loosened, and immediately it was made very good. Then we tried with some lower objects, and it was good, almost equally good, there. For Saturn it was very greatly superior to what it had been before. Still it is not satisfactory to us, and at this time a strong chain is in preparation, to support the mirror edgeways instead of the posts that there were at first or the iron hoop which we had on it yesterday. Nobody would have conceived that an edgewise gripe of such a mass of metal could derange its form in this way. Last night was the finest night we have had as regards clouds, though perhaps not the best for definition of objects. THE CASTLE, PARSONSTOWN, _1848, Sept. 2_. I cannot learn that the fault in the mirror had been noticed before, but I fancy that the observations had been very much confined to the Zenith and its neighbourhood. 1849