1^8 OCCULTATION OF A STAR BY MARS. 



will be more liable to be fcratclied and broken than thofe of 

 the common form, and when the frames are metallic, more 

 likely to increafe than diminifli tliat indelible mark made on 

 the nofe by the weight of the frame, fo frequently complained 

 of by perfons who wear fpedlacles almoft conftanlly. A great 

 deal of fuperfluous light alfo paffing through the glafTes, mufl 

 be evidently prejudicial; and, it appears to me that the con-» 

 cave figure of the inner fide of the menifcus will a6t as a 

 powerful reflector to condenfe the rays of light and heat upon 

 the eyes, and ultimately prove thereby of ferious injury. 



I have in my pofTeffion a menifcus I'pedacle glafs, taken 

 from a fpeiftacle frame, which 1 can prove to have been made 

 many years ago; and, finally, as this form is neither new 

 in principle, or in practice, I am at a jofs to know upon what 

 fort of difcovcry his Majefly^s letters patent have been fo- 

 licited. ' 



I am, I 



Sir, 



Tour's, &c. 



W. JONES. 



VIIL 



Jn Account of an Occultation of b Nebulae Sagittarii, by the 

 Planet Mars, on the 17 th of April 1796, obferved by Sir 

 Henry Englefield, Bart. F, U. S. In a Letter aiU 

 drejjcd to the Rev. Nevil MaskeIkYNe, />. D. f. R. S, 

 and Jftronomer Royal, * 



DEAR SIR 



bccukatiou of a J[ BEG leave to communicate to you an obfervation, which 



planetMarsV ^ ^ ^^^ ^^'^ g^^^^ fortune to make, of an occultation of a fixed 



flar by the planet Mars ; and which, as far as lean learn, 



was feeii by nobody in this country but myfelf and Lady Buck, 



at whofe houfe at Peterfliam I made the obfervation, and to 



whom I fliowed the planet when nearly approaching to con- 



jun6iion with the ftar. 



•Thefe obfervn- Obfervations of this kind may be ranked ^mong the rareft 



tions are very phenomena in afironomy. Mr. De La Lande records but 



jarc. * 



♦ From the Journals of the Royal Inilitution, No. 16, p. 38* 



four 



