REPORT OF THE &EW COMMITTEE. XXXV11 



object-glasses would suffice to include the rays proceeding both to the index 

 and to the horizon-glasses of large sextants, Mr. Cooke employs double colli- 

 mators of moderate size ; and he adjusts each pair to strict parallelism by 

 aid of a detached telescope. 



The coloured shades of the sextant are readily examined by strongly illu- 

 minating the fields of two of the collimators, after contact of their cross wires 

 has been made in the ordinary manner. 



On the application of Mr. Galton, backed by the recommendation of the 

 Kew Committee, the Council of the Eoyal (Society has allotted .£80 from the 

 Government Grant, to defray the estimated cost of Mr. Cooke's apparatus, 

 and its establishment in the Observatory at Kew. 



The apparatus will be erected in the basement-hall of the Observatory; 

 and when the arrangement is complete it is hoped that the Observatory will 

 become a place where quadrants and sextants can be verified with great 

 facility, and where scientific travellers or officers in Her Majesty's Service 

 may receive instruction in the use of geographical instruments. 



The solar spectrum is being mapped by the spectroscope belonging to the 

 Chairman. All the measurements for the region between D and E have 

 been made and carefully verified ; and a map of this region, in accordance 

 with these measurements, has been constructed by Mr. Loewy. Many more 

 lines are exhibited in this map than in that lately made by Professor Kirch- 

 hoff. Observations made by this instrument have likewise brought out 

 several new lines in the spectrum of ignited sodium. 



At the joint suggestion of Professor Tait of Edinburgh and the Superin- 

 tendent, an ingenious apparatus has been constructed by Mr. Eeckley, by 

 means of which a disk can be made to revolve in vacuo with great velocity ; 

 and a short description of some experiments performed by means of this 

 instrument, with the view of ascertaining whether visible as well as mole- 

 cular motion is dissipated by a medium pervading space, has been commu- 

 nicated to the Eoyal Society by the Superintendent in conjunction with 

 Professor Tait. 



The instrument devised by Mr. Broun, for the purpose of estimating the 

 magnetic dip by means of soft iron, remains at present at the Observatory. 



The Superintendent has received grants from the Eoyal Society for special 

 experiments ; and when these are completed, an account will be rendered to 

 that Society. 



It will be seen from the foregoing Eeport, that many other experiments 

 and observations, of a nature to advance science, are made under the sanc- 

 tion of the Committee, besides those which form the ordinary work of the 

 Observatory; it is, however, always stipulated that the cost of such experi- 

 ments shall be defrayed by their promoters. 



J. P. Gassiot, 



C hairman. 

 Kew Observatory, 



31st August, 1865. 



