CONTENTS. IX 



Page 



X. NINTH LETTER ON GLACIERS. Addressed to PROFESSOR 



JAMESON [1845] 68 



Remarks on the Recent Observations made on the Glacier 

 of the Aar (in 1844) by direction of M. Agassiz...New Con- 

 firmation of the Plastic Theory.... Condensation of the 

 Glacier in its downward course in consequence of Frontal 

 Resistance... Continuity of Motion... Motion accelerated in 

 Fine Weather Excess of Central Velocity of the Glacier 

 ...Motion of Glaciers of Second Order, and of Snow Beds. 



XL ILLUSTRATIONS OP THE Viscous THEORY OF GLACIER 

 MOTION.* PART I. CONTAINING EXPERIMENTS ON THE 

 FLOW OF PLASTIC BODIES, AND OBSERVATIONS ON THE 

 PHENOMENA OF LAVA STREAMS [1845] . . .77 



1. Plastic Models. 2. Analogy of Glaciers to Lava 

 Streams... Note on the Velocity of Lava, 



XII. ILLUSTRATIONS OF THE Viscous THEORY OF GLACIER 

 MOTION.* PART II. AN ATTEMPT TO ESTABLISH BY 



OBSERVATION THE PLASTICITY OF GLACIER ICE [1845] 95 



3. De Saussure's Theory. 4. Modifications of De Saus- 

 sure's Theory. 5. Experiments at Chamouni on the 

 Plasticity of Ice. 



XIII. ILLUSTRATIONS OF THE Viscous THEORY OF GLACIER 



MOTION.* PART III. [1846] . . . .119 



6. On the Motion of Glaciers of the Second Order. 7. On 

 the Annual Motion of Glaciers, and on the Influence of 

 Seasons. 8. Summary of the Evidence adduced in favour ^ 

 of the Theory... Glacier not a Mass of Fragments... 

 Argument from the Equable Progression of Glaciers... 

 Formation of Crevasses... Law of Velocities... Ablation of 

 the Surface... Plasticity ; Veined Structure. 



Addition on the Plasticity of Ice on the Small Scale 167 

 * From the Philosophical Transactions. 



