XX 



CONTENTS, 



city ; Mcasuremtnts of degrees ; 569. Zones ; 570. 

 Climates; Sea and land; Continents; 571. Rivers; 

 Elevations; 572. Mountains; 573. DifFcrent orders 

 of mountains; Internal parts of the earth; 574. Den- 

 sity of the earth ; 575. 



Lecture xLvii. On the tides; 

 576. 



Tides noticed by the ancients ; Daily changes ; 570. 

 Monthly changes; Yearly clianges; Connexion with 

 the moon; Effect of gravitation on a fluid sphere; 

 577. Primitive lunar tides; Comparison with a pen- 

 dulum ; 578. Direct and inverted tides ; Tides of a 

 lake; 579. Resistance; Tides of the Atlantic ; 580. 

 Particular modifications ; 58 1. Tides of t'.ie Channels, 

 and of rivers; 582. Inferior and superior tides ; Laws 

 of elevation and of depression; 583. Mode of ob- 

 serving the tides; Solar tides; Combination of tides; 

 584. Retardation of spring and neap tides; 585. 

 Increased height in converging channels; Combina- 

 tions in particular ports; 586. Currents; Tides of the 

 atmosphere ; 587, 588. See corrections. 



Lecture xlviii. On the history 

 of astronomy ; 589. 



Earliest astronomy ; Signs of the zodiac; 589. Baby- 

 lonian observations; Chaldeans; Hermes; Egyptians; 

 Chinese; 590. Indians; Greeks; 591. Thales; Py- 

 thagoras; Meto; Alexandrian school ; 592. Erato- 

 sthenes; Hipparchus; 593. Ptolemy; 594. Arabians; 

 Persians; 595. Copernicus; Tycho Brahe; 596. 

 Kepler; 59T. Napier; Huygeus; Cassini; Gravita- 

 iJon; 598. Newton's discoveries; Extract from Pem- 

 berton; 599,600. British astronomers ; Observatory 

 at Greenwich; 001. Determination of the longitude ; 

 Late discoveries; 602, 603. See corrections. Chrono- 

 logical table ; 004. 



Lecture xlix. On the essential 

 properties of matter ; 605. 



Importance of minute objects; 605. Definition of 

 mater; Place of the investigation; 006. Essential 

 and accidental properties of matter; Extension; Di- 

 visibility; 607. Actual division of matter; 608. 

 Impenetrability; 609. Permeability; Orders of sub- 

 stances; 610. Repulsion; Apparent contact; 611. 

 Laws of repulsion; 612. Dalton's hypothesis; Re- 



pulsion of liquids and solids; Reciprocality of repul- 

 sion; 613. Inertia; Gravitation; Cause of gravita- 

 tion; 614. Mathematical conceptions; Newton's 

 opinion; 615. Constitution of a medium capable of 

 producing gravitation; 616. Difficulties; 617. 



Lecture l. On cohesion ; 618. 



Accidental properties of matter; Laws of cohesion ; 

 618. Modification of cohesion by heat; Liquidity; 619i 

 Superficial cohesion; 620. Bubbles; Form of the sur- 

 face of a fluid ; 021. See corrections. Magnitude of the 

 force of cohesion; Ascent between two plates; 622. 

 Capillary tubes ; Horizontal surface ; 623. Detached 

 portion of a liquid ; Lycopodium ; Attractions and re- 

 pulsions of floating bodies; 024. Apparent cohesion 

 of plates ; Drop between plates; Oil spreading on 

 water; Sponge; 025. Long column supported by 

 cohesion; Cohesion of solids; More perfect union; 

 026. Solidity; 627. Cause of solidity ; Elasticity;. 

 028. Stiffness; Strength; Softness; Ductility; 629. 

 Primary cause of cohesion; 630. 



Lecture li. On the sources and 

 effects of heat; 631. 



Division of the subject of heat ; Definition of heat 

 and cold; 631. Excitement of heat; Condensation; 

 Friction ; Count Rumford's experiments ; 632. Ef- 

 fect of velocity ; 633. Pictet's experiments ; Heat 

 from combustion ; 634. Communication of heat i 

 Conducting powers; Fluids; 635. Radiation of heat; 

 Mr. Leslie's discoveries ; 636. Differences of solar 

 and culinary heat ; Invisible heat ; Equilibrium of ra- 

 diant heat ; 637. Apparent reflection of cold ; Re- 

 frangibility of heat ; 638. Blackening rays ; Effects 

 of heat; Tejnporary effects; 639. Expansion of 

 gases; Condensation; 640. Expansion of fluids; 

 Diminution of cohesive powers; Boiling; Slow eva- 

 poration; 041. Contraction; Freezing; Expansion 

 of solids; 042. Liquefaction; Cracks from heat; 

 043. Permanent effects of heat; Glass drops; Tem- 

 pering of metals ; 644, 645. 



Lecture lii. On the measures 

 and the nature of heat ; 646. 



Measures of expansion; Pyrometer; Scale of heat; 

 646. Mixtures; Sun's rays; Expansion of solids and 

 fluids; Tiiermometers ; 647. Wedgwood's thermo- 



