StiigiJaf Jppeafanet if the Ceajt of France by RefraB'ton. 'jpf '^ 



ffiateTy be fhewn ; it would be ufelefs to add to the number of experiments, which would ' 

 convey no otlicr information than is already known concerning the phofphate of lime. 



In order to eftabllfh the proportions of phofphoric acid and lime in the chryfolite, It 

 muft be recolIe£ted, i. that loo parts of this fubftance aiFordfd in the fecond experiment 

 Il6 parts of calcined fulphate of lime, which, according to Bergman, contained 48,84. 

 of pure lime : 2. that there remained 1 1 parts of phofphate of lime not decompofed,, 

 which were capable of forming 14,33 °^ fulphate of lime, which added to the 116 give 

 J3C'>33- Now if 116 contain 48,84 of Hme, it is evident that 130,33 muft contain 53,32. 

 According to this experiment, therefore, 100 parts of chryfolite contain 53,32 of lime ; and 

 fubtradting this from the 100, there will remain for the phofphoric acid 46,68. In the 

 third experiment it is alfo feen, that 100 parts of chryfolite, diflblved in the muriatic 

 acid, afforded by the oxalic acid 1 1 8 parts of oxalate of lime ; and that thefe 1 1 8 parts left 

 after calcination 54,28 parts of pure hme, which fubtradted from 100, give 45,72 for the 

 phofphoric acid. 



We fee, therefore, that the refults of thefe two experiments do not diflfer fo much as 

 one hundredth part from each other, and that they perfeftly agree with the component 

 parts obtained by Klaproth in his analyfis of the apatite, from which he obtained 55, parts 

 ©f lime and 45 of phofphoric acid. 



X. 



Account of a fingular Injiance af Atmofpherical RefraSlioii. In a Letter from JVlLLIAM 



Latham, Ef^. F.R.S. andJ.S. tn the Rev. H. Whitfield, D.D. F.R.S, and A.S* 



O 



Dear Sir, Haftings, Auguft i, 1797. 



N Wednefday laft, July 26, about five o'clock in the afternoon, whilft I was fitting in 



my dining-room at this place, which is fituated upon the parade clofe to the fea-fliore, 



nearly fronting the fouth, my attention was excited by a great number of people running 



down to the fea-fide. Upon enquiring the reafon, I was informed that the coaft of France 



was plainly to be diflinguifiied with the naked eye. 1 immediately went down to the fhore„ 



and was furprifed to find that, even without the afiiflance of a. telefcope, I could very plainly 



fee the cliffs oi^the oppofite coaft; which, at the nenreft part, are between forty and fifty miles 



diftant, and are not to be difcerned„ from that low fituation, by the aid of the beft glafles. 



They appeared to be only a few miles off, and feemed to extend for fome leagues along the- 



coaft. I purfued my walk along the fhore to the eaftward, clofe to the water's edge, con- 



verfing with the failors and fiftientien upon the fubjeft. They, at firft, could not be per- 



fuaded of the reality of the appearance ; but they foon became fo thoroughly convinced, by 



tlie cliffs gradually appearing more elevated, and approaching nearer, as it were, that they 



pointed out, and named to me, the different places they had been accuftomed to vifit ; fuch 



as, the Bay, the Old Head or Man, the Windmill, &c. at Boulogne ; St. Vallery, and other 



places on the coaft of Picardy ; which they afterwards confirmed, when they viewed them. 



through their telefcopes. Their obfervations were, that the places appeared as near, as if. 



tlaey were failing, at a fmall diftance, into the harbours. 



* Philof. Tr'Hf- '798, page 35;. 



Having; 



