INDEX. 



Natural philofophy, queftion refpeftlng Us 



progrefs, 160 

 Newcomen and Cowley's atraofpheric en- 



gme, 313 

 l^cwton, Sir I. 10a • 



f)aks, great importance of the culture of, 

 17— Are erroneoufly fuppofed to be of 

 flow growth, 18— Their magnitude may 

 be doubled by culture, 19 — Pradlical 

 direftions for their management, ib.— 

 Proofs of its fuccefs, 2Z 



Occul^tion of a fixed ftar by the planet 

 Mars, 198 



Pils, probably decompofe water and air, 

 123 — Rancidity promotes their uqion 

 with mercury, ib.— Eftedls of, in time- 

 keepers, 204— Atlionof cold on, 205 



•— — eflential, procefs for purifying them 

 when rancid, 68 — Theoretical fpecula- 

 tion, 69— Subf^quent experiment, 70 



Olbers, Dr. his merit as an aftronomer, 



159 



Pptical queftions, 71, 236 



Palladium, reward for the artificial pro- 

 duction of, 75, 159 — Prefumed fo be 

 an alloy of the new metal, difcovered in 

 the ore of platina, with mercury, 76— 

 Inquiries concerning, 85 — General pro- 

 perties of, 86 — Chemical examination 

 of, 87 — Specific gravities of its alloys, 

 89— Beautiful red folution in acids, 90 

 — Coraparifon with other metals, 91— 

 3s an alloy of platina and mercury, ib. 

 —Synthetical proofs, 9a— General in- 

 ferences, 96— Its analyfis extremely 

 difficult, 97 — Analytical experiments, 

 98— Objections to the name, 99 — 

 French opinion refpetling its compofi- 

 tioD, 11% 



Paper, advantagcoufiy employed as a rub. 

 ber for eledrical machines, 126 



Papin, excellence and utility of his di- 

 gefter, 161— Improvement in the mode 

 of clofing it, 162— His fteam engine, 

 3" 



Parkinfon, Mr. 320 



Pafteboard, its ufe iti the galvanic pile, 

 288, 303 



Peale, Mr. C. W. 284 



Pendulum rods of lead and iron, 300 



Pen-knife, a large one moft ufeful, 300 



Pennant, Mr. 279 



Pepys, Mr. 96 



Perifcopic fpeftacles, propofed as a reme- 

 dy for the defeats in common ones, 146 

 —Objected to, 192 — Experiment prov- 

 ing the advantages of, 241 — Obferva- 

 tions on, 291 



Philofophy, natural, queftion refpeCting 

 its progrefs, 160 



Phofphorus and fulphur, method of unit- 

 ing without danger to the operator, 58 



Picket, 6 



Pile, galvanic, the fecondary differs from 

 the common only in intenfity, 289— 

 With ice, 303 — With air interpofed 

 inftead of wet bodies, 305 — Its aCtion 

 on cloth dlflcs, 320 



Pifo, 277 



Platina, a new metal difcovered in its ore, 

 76, 117 — Method of uniting it with 

 mercury, 9a — Experiments on, 178 — > 

 Muriate of tin, the moft delicate teft, 

 of, 179 — .Order of its affinity with the 

 acids, 180 — Application of it on porce- 

 lain, 286 



Piayfair's, Mr. inveftigation of theorems 

 relative to the figure of the earth, 67, 

 102, 177 



Porcelain, procefs for applying platina on 

 it, 287 



Potter, Humphrey, 314 



Powder, dangerous fulminating, 77 



Prefs with a double fcrew, defcription of, 



51 



Principlcjt 



