Mr Ritchie on Leslie a Photometer. 321 



gun comes into the proper position to be fired. Thus, by 

 giving the left hand more to do, than in the ordinary gun, and 

 therefore proportionally easing the right hand, the writer 

 thinks, the gun will be held more steadily to the shoulder, a 

 surer aim be taken, and greater execution done, than with the 

 gun in common use, and in the ordinary mode of firing. 



Lastly, a loaded gun may be rendered perfectly safe, when 

 lying in a house, or entrusted to servants, or in the hands of 

 ignorant persons, by merely taking off the key ; for then the 

 machinery that works the locks cannot be reached, and conse- 

 quently the gun cannot be discharged.* 



Manse ofCurrie, 28th Feb. 1825. 



Art. XXVII. — On Leslie's Photometer, and its application to 

 determine the relative Intensity of the Sun's Rays, and the 

 Illuminating Powers of Coal and Oil Gas. By William 

 Ritchie, A. M. Rector of the Academy at Tain. Com- 

 municated by the Author. 



The differential photometer of Professor Leslie has lately ex- 

 cited so much discussion, and has been so much the subject 

 of conversation, that a fair and impartial account of its 

 merits and defects cannot fail to be acceptable to the generali- 

 ty of readers. Those who defend the accuracy of the instru- 

 ment are so lavish in its praise, that we may fairly conclude 

 they have neither carefully examined the principles on which 

 it is founded, nor the inaccuracies to which it is evidently lia- 

 ble. Those, on the contrary, who espouse the opposite side 

 of the question, are so liberal in their condemnation of it, that 

 we are led to suspect they have exaggerated its defects. At 



* All guns, new and old, single and double, flint and percussion, are, 

 at a small expence, susceptible of this improvement; and various speci- 

 mens of them, so fitted up, may be seen at Mr William MaclachJan's, 

 gun-maker, No. 39, Nicholson's Street, and at Mr John Thomson's, gun- 

 maker, No. 3, South St Andrew's Street, Edinburgh, agents for the in- 

 ventor. For England any farther information will be given on this subject, 

 by Mr Robert Wheeler, gun-manufacturer, Birmingham, who has made 

 arrangements with the patentee, both for fitting up guns on this principle, 

 as well as supplying the trade in England 



VOL II. NO. II. AI'KIL 1825. V 



