202 Altitudes of the Sun [May, 



it will at least produce in men of property that sympathy for the objects 

 of scientific men, which will ensure them the means of applying all their 

 faculties to the best advantage. All wealthy men are as much bound 

 to dispense a portion of their revenues in the promotion of science, and 

 in every other noble and generous enterprize, as the Government under 

 which they live. Let them therefore be called upon to rouse them- 

 selves for the more extended performance of this duty. And let those 

 who enjoy such honours and emoluments as science already possesses, 

 shew by their superior diligence and success, that there is some virtue 

 in the secular advantages which they possess, raising them as scientific 

 men above those who are destitute of them, before the dangerous experi- 

 ment be made of increasing such stalls and dormitories. 



There appears to me something so portentous in this matter, that 

 I should like to see it fully discussed upon principles that approve 

 themselves to sound reason. But I must leave it to abler hands. 



I am, Sir, &c. &c, 



J. Mack. 



[On this subject Ave refer our readers to the valuable remarks of M. Biot, 

 inserted among the Scientific Intelligence of the present number. — Ed.] 



VII. — Memoranda regarding the Difference between Morning and 

 Evening Altitudes, for Ascertaining the Apparent Time on board 

 ship. By Captain D. Ross, Marine Surveyor General. 

 With most navigators, when quitting a port, it is usual to ascertain the 

 deviation of the chronometer from mean time by altitudes of the sun 

 taken either on shore with an artificial horizon, or by that of the sea 

 from on board ship. These altitudes are generally taken before noon, and 

 seldom, I believe, is the deviation of the chronometer ascertained by 

 altitudes taken in the afternoon ; but from the long experience I have 

 had, I am led to believe, that to approximate to accuracy, it is right that 

 altitudes should be taken on each side of the meridian at the place of 

 departure ; for it will be found that in cases where the difference of longi- 

 tude between it and a distant station is to be measured, if the result of 

 altitudes taken at the latter in the afternoon be compared with those 

 taken in the forenoon at the point of departure, they will frequently 

 give a longitude differing two or three miles from a deduction of the 

 same measurement made by comparing two forenoon observations 

 together, and in such cases, there may be an uncertainty to that amount, 

 in fixing the position of a rock or other danger. If at the point of 



