subtended, though of less magnitude, are still remarkably constant, as we {597} may see by Fig. 313; where the angle subtended by each chamber is made equal to 20ô¯, and this diagrammatic figure is not perceptibly different from the other. In some cases the subtended angle is less constant; and in these it would be necessary to equate the several linear dimensions with the corôÙreôÙsponôÙding vector angles, according to our equation r =ã₤eÿ£¢ö¡ã₤cotã₤öÝã₤. It is probable that, by so taking account of variations of ö¡, such variations of r as (according to Rhumblerãs measurements) Pulvinulina and other genera appear to shew, would be found to diminish or even to disappear.