CONTENTS. ix 



I. Farther Experiments and Obfervations on the Aflfefllons and Properties of 

 Light. By Henry Brougham, jun. Efq. — — — P- ^93 



Oa the colours produced by the irregularities of fpecula of metal and of glafs, &c. — Conclufion. 

 Phenomena of Iceland ciyftal, not produced by refraftion or flexion. Conjefture refpefting it. 

 General propofilions. 



II. Obfervations on Bituminous Subftances, with a Defcription of the Varie- 

 ties of the Elaftic Bitumen. By Cliarles Hatchett, Efq. F.R.S. Load, 

 and Edin. F.L.S. &c. — — ■— — p. 201 



Enumeration and defcriptions of bitumens j naptha; petroleum; mineral tar; mineral pitch; af- 

 j^ phaltum ; jet ; pit-coal ; bituminous wood ; turf; peat ; and bituminous ores. Gradations from 

 naptha to afphaltum occafioned by the proportion of carbone becoming greater in confequence of 

 the efcape of other principles. The flow combuftion of pit-coal depends not only upon the nature- 

 of the component parts, but the intimacy of their union. Fafts and obfervations rcfpefting bitumi- 

 nous wood, turf, and peat, and the developement of carbonej in vegetable matter^ during the change 

 it undergoes in the bowels of the earth. 



III. New Methods of affording, at an inconfiderable Expence, the Heat and 

 tlie Water required for performing Experiments in Chemiftry. By Citizen 

 Guyton — — — ■ — . — p. 209 



, Great advantage of fimplicity in experiments exemplified in thofe of Franklin and Bergman. De- 

 fcription of a very ufeful lamp furnace. Almoft every operation in chemiflry performed by this 

 apparatus with great fpeed, precifion and perfpicuity. Inftances. Pure water an objeft of the 

 firit neceffity in chemical refearches. Many experiments are neglefted, or inaccurately performed, 

 for want of a fufficient quantity of this fluid. Rain water coUefted from the roofs of houfes after 

 the firft {hower has waflied the furface, contains no impurity but phofphate of lime, and a portion 

 of earthy matter mechanically fufpended. The latter is removed by immediate filtration, and the 

 former by a Iblution of pure barytes. This earth forms an inibluble precipitate with the fulphuric 

 acid, and leaves the lime partly dilTolved ; which likewife falls down by abforption of carbonic acid 

 from the atmofphere, or by the defigned addition of a portion of pure water impregnated with that 

 principle. The depuration of water by barytes promtfes to be of great utility in the art of dyeing 

 and other proceffes. 



IV. An Account of fome Experiments made by Mr. John Cuthbertfon, with 

 a View to determine an unequivocal Method of afcertaining the Power of 

 Eledrical Machines . — — — — P-2i5 



Meafures of ele61ricity, by the fiiark, by the charge, and by attrailion. Inconveniences of each. 

 Modifications of the rule for eftimating eleftrical charges. New method of mealiiring eleftricity by 

 the explofion of wire. Experiments. ' " 



V. Mincralogical Defcripticjjgi j^f G.ibraltar. By Major Imrie. (Concluded.) 



, '''\^:'".:i ,V. p. 2.19 



Obfervations. — Account of the foflil bones found in the Rock of Gibraltar. Their origin. 



VI. Accounts of the Difcovery of Native Gold in Ireland — p. 223 



Situation of the gold mine, Hlftorical fafts refpcifling it. Mineralogy of the country. Particular 

 account of the auriferous ftream, the wtn-lungs, and the late produce. ".c ,)'i/.l 



. Vol. II. — March 1799. « VIK'Ka 



