138 Analyses of Books, [Aug. 



our bodies a current of moist air, which is then felt in propor- 

 tion to the rapidity with which we pass through it. If it were 

 thought worth while to bring this to the test of the thermome- 

 ter, the instrument should be made to pass through the air at 

 the same rate as the person would move." 



VI I. On the Transit Instrument of the Cambridge Observatory, 

 fteing a Supplement to a former Faper ; by Robert Woodhouse, 

 Esq. Plumian Professor of Astronomy in the University of 

 Cambridge. 



VIII. Account of a Series of Observations made in the Summer 

 of the Year lS25,for the Purpose of deter mining the Difference of 

 Meridians of the Royal Observatories of Greenwich and Faris ; 

 drawn up by J. F. W. Herschel, Esq. MA. Sec. RS. : commu- 

 nicated by the Board of Longitude. 



The following is Mr. Herschel's account of the manner in 

 which these observations were made : 



" Operations having been carried on to a considerable extent 

 in France, and other countries on the Continent, for the purpose 

 of ascertaining differences of longitude by means of signals, 

 simultaneously observed at different points along a chain of 

 stations ; and the Royal Observatory at Paris, in particular, 

 having been connected in this manner with a number of the 

 most important stations, it was considered desirable by the 

 French government that the Royal Observatory at Greenwich 

 should be included in the general design. The British Board 

 of Longitude was accordingly invited to lend its co-operation 

 towards carrying into effect a plan for that purpose ; and the 

 invitation being readily accepted on their part, I was deputed, in 

 conjunction with Captain Sabine, in the course of the last sum- 

 mer, to direct the practical details of the operation on the British 

 side of the channel, and to make the necessary observations. 

 Every facility was afforded us in making our dispositions, on the 

 part of the different branches of His Majesty's government to 

 which it was found necessary to apply. A detachment of artil- 

 lery was placed, by his Grace the Duke of Wellington, Master 

 General of the Ordnance, under the orders of Captain Sabine. 

 Horses, waggons, and men, were furnished for the conveyance 

 of a tent, telescopes, rockets, and other apparatus ; and four of 

 the chronometers belonging to the Board of Admiralty were 

 placed at our disposal. The rockets required for making the 

 signals were furnished us from France. It would have been 

 easy, doubtless, to have procured them from the Royal Arsenal 

 at Woolwich ; but on the representation of Colonel Bonne, to 

 whom the principal direction of the operations in France was 

 intrusted, it was thought more advisable to accept an offer made 

 to us of any number which might be required, prepared at Paris 

 expressly for similar operations, carrying a charge of eight 

 ounces of powder, the instantaneous explosion of which, at 



