No. 6.
No. 7.
No. 8.
PREFACE.
Every effort of human ingenuity professing to remove or lessen pain and inconvenience, is, naturally enough, hailed with approbation, and the public require not so much to be aroused to estimate fully the advantages proposed, as to be guarded against implicit belief and heedless confidence in the value and importance of the remedy. It is, however, of the utmost importance to be accurately informed what kind of benefit we may fairly expect from the use of the given means, and to what extent this benefit may be obtained; and yet the man who steps forward to state this plainly and fairly, too often fails of the success which his undertaking deserves. Experience proves that such endeavours have been contemned by some, looked upon with cold indifference by others, and viewed with suspicion by nearly all. We are too apt to suspect interested motives, to doubt the sincerity, and undervalue the abilities of men, who have devoted their lives, and the force of their talents, to a particular pursuit; and then, as though this cunning incredulity was closely allied to implicit credence in the wildest chimeras, we become ready listeners, and passive victims, to pompous and plausible charlatans, who make the largest promises, alike indifferent to the practicability or usefulness of their specifics. “It is a great mistake,” said an able English statesman of the last century, “to suppose men harmless because they are blockheads; the dunce thinks neither of country nor of consequences in the pursuit of his petty interests and passions, which may, and often do, lead him to work the greatest public calamities.”
I have refrained from advancing any crude theoretical opinions, which might fairly be questioned. The information conveyed in these pages is of a practical character; has stood the purifying test of time; and, being based upon the immutable principles of optical science, courts every enquiry and challenges all investigation.