138 Royal Astronomical Society. 



and no one can positively say, or even reasonably suppose, that the 

 whole manufacture is not capable of great improvement. 



An attempt has been made by Mr. Simms to furnish the object- 

 glass for the Liverpool equatoreal from his own workmanship ; but 

 the indifferent quality of all the optical glass which is on sale (the 

 Munich unworked glass is not to be bought) did not allow him to 

 fittain the degree of perfection which he aspired to. In this di- 

 lemma, the Town Council have requested the Astronomer Royal to 

 purchase the object-glass, tube, and eye-glasses, from Mcrz and Co. 

 of Munich. The mounting which the Astronomer Royal proposes 

 to adopt is that sometimes called the English mounting, — namely, a 

 transit telescope between two supports, which, united at the top and 

 bottom, form the polar axis. Mr. Airy considers that by making 

 these supports of sheet-iron, having a section something like that of 

 a chord and arc, he will get great stiffness and solidity with moderate 

 weight, and at a comparatively small expense. When thus equipped, 

 the Liverpool Observatory will doubtless furnish a plentiful supply 

 of valuable extra- meridional observations. This excellent institu- 

 tion will then be a model of what the science may reasonably look 

 for at the hands of those who attend to the interests of navigation 

 at the principal ports, — namely, ample means of giving time and 

 regulating chronometers, with power to the superintendant of em- 

 ploying the time he has to spare about that class of observations in 

 which a private observer can make himself really useful to the pro- 

 gress of the science. 



It was mentioned in last year's Report that Mr. Sheepshanks had 

 undertaken to finish the construction of the standard yard measure 

 commenced by Mr. Baily. On examining the state of progress (for 

 Mr. Baily's last illness seized him when he had hardly commenced 

 his operations) and the points which were left not satisfactorily de- 

 termined by preceding measures, Mr. Sheepshanks, with the consent 

 of the Committee, resolved upon a more extensive series of experi- 

 ments than was at first contemplated. It was found by the officers 

 of the Ordnance survey, and by Mr. Simms when repeating the ope- 

 ration, that the hypothesis of equal expansions of metals for equal 

 increments of temperature, as shown by the mercurial thermometer, 

 is far from exact. Mr. Baily's preliminary measures also showed 

 that the differences between certain standards had varied sensibly 

 since the time when he constructed the standard scale of the So- 

 ciety. The method of properly supporting a bar has been recently 

 considered by the Astronomer Royal, in a paper contained in our 

 newly-published volume. This is not a proper place or time for 

 entering upon the details of processes which must be tried before 

 they are approved of. The apparatus is well-advanced, and the ob- 

 jects proposed are, to ascertain the best material for a measure, with 

 the law of expansion of the material ; to perpetuate the measure 

 itself, although the material may undergo slow changes from mole- 

 cular action ; and to leave commencing data for a more complete 

 inquiry into the subject, to be made in another generation. Mr. 

 Sheepshanks, up to this time, sees no reason to doubt of success, 



