330 REPORT— 1841. 



progress in constructing a map of the spectrum, containing the numerous 

 lines and bands produced by the action of nitrous gas. 



In submitting to examination several other gaseous media, my results have 

 been principally of a negative character ; but in my experiments with solid 

 and fluid media, I have been led to positive and interesting results. 



In order to obtain additional accuracy of observation, particularly near the 

 extremities of the spectrum, Mr. Dollond has constructed for me some im- 

 portant pieces of apparatus for directing and condensing the solar rays ; and 

 I have recently obtained from Mr. Merz of Munich, a yery large prism, to 

 be used vi'ith the telescope, and a series of smaller prisms for constructing a 

 prismatic cylinder for the purpose of expanding or magnifying particular 

 parts of the spectrum. D. Brewster. 



St. Leonard's, St. Andrew's, July 26th, 1841. 



The Committee appointed to superintend the reduction of the stars in tJte 

 Histoire Celeste, report — 

 That, at the last meeting of the British Association, they stated that it 

 would cost about 200/. more than the sum then expended, to complete the 

 whole of the reductions. That some error appears to have taken place in 

 the amount of the grant, as only 150Z. was appropriated, of which 135/. has 

 now been expended, thus leaving 15/. in hand. The Committee, therefore, 

 again suggest the propriety of extending the grant, this year, to (551., which 

 will complete the original estimate for the whole of the reductions, and which 

 can thus be finished before the next meeting of the Association. 



Francis Baily. 



The Committee appointed to superintend the extension of stars in the Ttoyal 

 Astronomical Society's Catalogue, report — 

 That no delay has taken place in prosecuting the work, and that it is ex- 

 pected to be completed in a short time. That 40/. has been expended out 

 of the 150/. granted at the last meeting of the British Association ; and con- 

 sequently that there is 110/. still in abeyance, which the Committee request 

 may be continued till the completion of the work, in order to meet any 

 contingent expenses. Francis Baily. 



On the subject of Researches concerning the Mud of Rivers, the fol- 

 lowing notice has been received from Mr. J. Bryce, Jun. 



Maghera, County of Londonderry, July 19, 1841. 

 I HAVE received from the Treasurer 51. of the grant, of which I have ex- 

 ])ended about 1/. in commencing the inquiry ; but owing to the construction 

 of a coffer dam, and other obstructions in the river at Belfast, preparatory to 

 the erection of a new bridge, I have not yet been able to obtain any result 

 which would be worth communicating to the Association. If, however, the 

 grant be renewed, I shall continue my inquiries vigorously after my return 

 to Belfast, during the autumn and winter. 



Nothing has been done by the other members of the Committee, as I retain 

 possession of the vessel which we use for raising the water. 



I am, dear Sir, faithfully yours, 



Jam£s Bryce, Jun. 



