The most singular part of this strange delusion is the fact of its strong hold on the minds of its infatuated votaries. Once bewitched with the idea of at last succeeding in the attainment of his grand design, fortune, health, and reputation, are resolutely set at nought, in the delirium of delight that follows; and more unreasonable creatures can scarcely be found than such self-deluded individuals, for they cannot, or will not, be convinced that their utmost efforts can at best but produce an amazingly curious toy; and nothing can be more futile than to expect any higher application, assuming such a discovery were possible. The best proof of the sincerity and earnestness of those who seek the attainment of a mechanical perpetual motion, is afforded by the variety and number of their patented schemes; the patentees having among them divines, doctors, lawyers, civil engineers, carpenters, draughtsmen, jewellers, watchmakers, shoemakers, confectioners, and all classes of professions and trades. It is not, as is generally supposed, only the wholly ignorant and designing who can be cajoled by these chimeras; there is in them a spice of mystery, of wonder, of singularity, and of simplicity combined with much subtle difficulty, which, being once fully imbibed, acts like an opiate draught. We have thus reviewed summarily, chimeras which are mainly associated with Astronomy, Chemistry, Mathematics, and Mechanics, and which have swayed the human mind more or less from a period anterior to the Christian era. The list of this species of deceitful systems of pseudo-philosophy, and of profitless problems, might have been enlarged; but what has been advanced may suffice as a warning to the uninitiated to beware of blind guides and of visionary pursuits. Science has lost nothing by its professors exercising that degree of caution, which all classes of superficially learned men, affecting to possess original and valuable views on certain matters, call _prejudice_: which, in such cases, generally means no more than the natural aversion which the learned have for all attempts to place specious dogmas on a level with sound science. Such enthusiasts are generally men of no research or depth of thought, who obtain an imperfect acquaintance with subjects with which they are incompetent to grapple; and with whom it is, therefore, hopeless to contend. Delusion will have its day, and will as certainly decay, if not die out. Chimeras constantly spring up, and find ardent professors and crowds of easily led proselytes, even up to this very present time; so that although, undoubtedly with many--_Knowledge is power_: yet it is to be feared that far too large a proportion of mankind favour the delusion that--_Ignorance is bliss_. EXPLANATIONS OF THE PLATES. PLATE I.--FIGURE 1.