in a general sense, implies something that happens by accident, or that is not essential to its subject.

in philosophy, is applied to that effect which flows from some cause intervening by accident, without being subject, or at least without any appearance of being subject, to general laws or regular returns. In this sense, accident is opposed to constant and principal. Thus the sun's place is, with respect to the earth, the constant and principal cause of the heat in summer, and the cold in winter; whereas winds, snows, and rains, are the accidental causes which often alter and modify the action of the principal cause.

ACCIDENTAL Point, in perspective, is that point in the horizontal line where the projections of two lines parallel to each other meet the perspective plane.

ACCIDENTAL Colours, are those which depend upon the affections of the eye, in contradiction to those which belong to the light itself. The impressions made upon the eye by looking steadfastly at a particular colour are various, according to the single colour or combination of colours in the object; and they continue for some time after the eye is withdrawn, and give a false colouring to other objects. Mr Buffon has endeavoured to trace the connections which these accidental colours have with such as are natural, in a variety of instances. The subject has also been considered by De la Hire, and M. Epences; and M. d'Arcy has contrived a machine for determining the duration of the effects of light, and after several trials, finds that it continues about eight thirds of a minute.