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the original ftate of the globe as the prefent, though fo far re- 

 moved from it. At no period has its furface been traverfed in 

 fo many different dircdions, or its fhape and extent under its 

 different modifications of earth and water been fo nearly afcer- 

 tained, and the relative denfity of the whole fo accurately deter- 

 mined, its folid conflituent parts fo exadlly diftingnilhed, their 

 mutual relation, both as to pofition and compofition, fo clearly 

 traced, or purfued to fuch confiderable depths as within thefe laft 

 twenty-five years. Neither have the teflimonies that relate to 

 it been ever fo critically examined and carefully weighed, nor 

 confequently fo well underftood, as within the latter half of this, 

 century. 



The introdudion of teftimony into refearches merely philofo- 

 phical has been, I am well aware, objeded to by many, but in 

 the prefent cafe the objedion evidently originates in inattention 

 to its objed. All philofophical refearches are grounded either on 

 experiment or obfervation fingly or jointly, and the confequences 

 clearly deducible from them. Where recourfe cannot be had to 

 experiment, as in the prefent cafe, there obfervation fingly muft 

 be reforted to, but as objeds even of obfervation are not of daily 

 occurrence, and many of them mufl have exifted at diflant inters 

 vals of time and place, recourfe muft be had to its records and 

 confequently to teftimony. Aftrcnomy furnifhes us with a cafe 

 in point. This is a fcience purely philofophical, yet aftronomers 

 have never hefitated to admit the obfervations of an Hipparchus 



G g a or 



