Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 1, 1802).djvu/75

51&#93; A NE 1. Having a circular motion round the iron axis, and being fur- nished with a vane at the top, and an index at the bottom, as soon as the artificial cardinal points de- scribed on the round piece of wood on the pillar are fixed to tire cor- responding quarters of the heavens, it faithfully points out the quarter from which the wind blows, . 2. Being furnished with a ve- lum, or sail, elevated by the wind, along the arch of the quadrant, to an height proportionate to the pow- er of the column of wind pressing against it, its relative force and its comparative power, at any two times of examination, may be accu- rately taken. 3. By means of a spring fitted to the notches of the iron, with which the quadrant is shod, the velum is prevented from returning upon the fall of the wind ; and the instrument, without the trouble of watching it, ascertains the force of the highest blast, since the last time of examination. . This machine may be confidently depended upon, as the velum is hung so nicely, that it is susceptible of the most gentle breeze, and will also describe the force of the wind in a violent storm. There is, how- ever, reason to apprehend, that by exposing the anemoscope to all winds, especially to irregular blasts and squalls, for a length of time, it may become inaccurate. The ob- server ought, therefore, to take the tube with its vane and velum, in his hand, with a view to learn the force of the wind ; and, after having made his observation, he should return with the machine in- to the house, till the violence of the storm subside. . ANEURISM, in surgery, signi- fies a throbbing tumor, occasioned ANE Li by the dilatation or rupture of an artery : it consists of three kinds, viz. the true or encysted, the false or diffused, and the varicose. The true aneurism, when situ- ated near the surface of the bod)-, produces a tumor, at first small and circumscr ibed, but, when press- ed by the finger, it manifests a dis- tinct pulsation. By degrees it in- creases, and becomes more promi- nent ; still, however, the patient does not complain of any pain. As it grows larger, the skin turns more pale than usual, also more phleg- monous, or swollen, and at length assumes a livid and gangrenous ap- pearance. A bloody serum now oozes through the integuments ; the skin cracks in several places ; and the artery, being deprived of the usual resistance, discharges its blood with such velocity, as to occasion almost instantaneous death. The false aneurism consists of a wound or rupture of an artery, and, by the extravasation of blood, pro- duces a swelling of the contiguous; parts. If not improperly treated by constant and close pressure, it generally remains nearly of the same size, for several weeks. In- stances have occurred, where the blood has diffused itself over the whole arm in a few hours ; as, on the contrary, swellings of this kind have been months, nay, even years, in arriving at any considerable size. The varicose aneurism is that which arises from the puncture of an artery, and sometimes happens in blood-letting. This circumstance, it is hoped, will point out the ne- cessity of persons applying to regu- lar practitioners, who are acquaint- ed with the situation qf the blood- vessels, and not employing, as is too frequently the case, ignorant and unskilful pretenders, for the per- li 'J. formauce