A
PRELIMINARY DISSERTATION
ON THE
MECHANISM OF THE HEAVENS.
BY
MRS. SOMMERVILLE
PHILADELPHIA:
CAREY & LEA
1832
In order to convey some idea of the object of this work, it may beuseful to offer a few preliminary observations on the nature of thesubject which it is intended to investigate, and of the means that havealready been adopted with so much success to bring within the reach ofour faculties, those truths which might seem to be placed so far beyondthem.
All the knowledge we possess of external objects is founded uponexperience, which furnishes a knowledge of facts, and the comparison ofthese facts establishes relations, from which, induction, the intuitivebelief that like causes will produce like effects, leads us to generallaws. Thus, experience teaches that bodies fall at the surface of theearth with an accelerated velocity, and proportional to their masses.Newton proved, by comparison, that the force which occasions the fall ofbodies at the earth's surface, is identical with that which retains themoon in her orbit; and induction led him to conclude that as the moon iskept in her orbit by the attraction of the earth, so the planets mightbe retained in their orbits by the attraction of the sun. By such stepshe was led to the discovery of one of those powers with which theCreator has ordained that matter should reciprocally act upon matter.
Physical astronomy is the science which compares and identifies the lawsof motion observed on earth with the motions that take place in theheavens, and which traces, by an uninterrupted chain of deduction fromthe great principle that governs the universe, the revolutions androtations of the planets, and the oscillations of the fluids at theirsurfaces, and which estimates the changes the system has hithertoundergone or may hereafter experience, changes which require millions ofyears for their accomplishment.
The combined efforts of astronomers, from the earliest dawn ofcivilization, have been requisite to establish the mechanical theory ofastronomy: the courses of the planets have been observed for ages with adegree of perseverance that is astonishing, if we consider theimperfection, and even the want of instruments. The real motions of theearth have been separated from the apparent motions of the planets; thelaws of the planetary revolutions have been discovered; and thediscovery of these laws has led to the knowledge of the gravitation ofmatter. On the other hand, descending from the principle of gravitation,every motion in the system of the world has been so completelyexplained, that no astronomical phenomenon can now be transmitted toposterity of which the laws have not been determined.
Science, regarded as the pursuit of truth, which can only be attained bypatient and unprejudiced investigation, wherein nothing is too great tobe attempted, nothing so minute as to be justly disregarded, must everafford occupation of consummate interest and of elevated meditation. Thecontemplation of the works of creation elevates the mind to theadmiration of whatever is great and noble, accomplishing the object ofall study, which in the elegant language of Sir James Mackintosh is toinspire the love of truth, of wisdom, of beauty, especially of goodness,the highest beauty, and of that supreme and eternal mind, which containsall truth and wisdom, all beauty and goodness. By the love or delightfulcontemplation and pursuit of these transcendent aims for their own sakeonly, th