When it is remembered that the punching tool was guided solely by the hand and eye, and that three or more blows of the mallet had to be struck for every dot, some conception may be formed of the patience and accuracy needed to produce these tiny protuberances in perfectly straight lines, at exactly equal intervals and of absolutely uniform size.
His observations of the protuberances on the sun, made during the total eclipse on the 10th of July 1860, are included in the work of Madler on the eclipse, published in 1861.
In some Sphacelariaceae branches may appear at their inception as lateral protuberances of the apical cell itself.
The design was then beaten into relief from the back with hammers and punches, the pitch bed yielding to the protuberances which were thus formed, and serving to prevent the punch from breaking the metal into holes.
That Zeno and Cleanthes crudely compared this presentation to the impression which a seal bears upon wax, with protuberances and indentations, while Chrysippus more prudently determined it vaguely as an occult modification or " mode " of mind, is an interesting but not intrinsically important detail But the mind is no mere passive recipient of impressions from without, in the view of the Stoics.