The present is the ninth volume which the Author has presented to the public, and he indulges the hope that it will meet with the same favourable reception which his former publications have uniformly experienced. It was originally intended to conclude the volume with a few remarks on the _utility_ of astronomical studies, and their _moral_ and _religious_ tendency, but this has been prevented, for the present, in consequence of the work having swelled to a greater size than was anticipated. Should he again appear before the public as an author, the subject of discussion and illustration will have a more direct bearing than the present on the great objects of religion and a future world. _Broughty Ferry, near Dundee, August, 1845._ CONTENTS. PART I. ON LIGHT. INTRODUCTION. Necessity of light to the knowledge and happiness of all sentient beings--Its beautiful and enlivening effects--An emblem of the Deity--Provision made for its universal diffusion _page_ 1-7. CHAPTER I. GENERAL PROPERTIES OF LIGHT. Interesting nature of this study--Different hypotheses which have been formed respecting the nature of light--It radiates in straight lines--Moves with amazing velocity--Flows in all directions from luminous bodies--Duration of its impressions on the eye--Supposed to have a certain degree of force or momentum--Experiments in relation to this point--Its intensity diminished in proportion to the square of the distance--Its reflection from opake bodies renders objects visible--Intensity of reflected light--Subject to the law of attraction--Forms a constituent part of certain bodies--_Solar phosphori_, and the phenomena they exhibit--Produces certain effects on planets and flowers, exemplified in a variety of instances--Supposed to have an influence on the _propagation of sound_ _page_ 8-37 Reflections on the nature of light, and the multifarious effects it produces throughout the universe--A representation of the Divinity--Wisdom and Goodness of God displayed in its formation _page_ 37-40. CHAPTER II. ON THE REFRACTION OF LIGHT. Nature of refraction--Illustrated by experiments--Angle of refraction--Familiar experiments illustrative of refraction--Refraction explains the causes of many curious and interesting phenomena--Its effect on the heavenly bodies--On the twilight--Illustrated by figures _page_ 41-53. EXTRAORDINARY CASES OF REFRACTION IN RELATION TO TERRESTRIAL OBJECTS.