separated alpha from the horizon. in order to fix the angle obtained， he fastened with thorns the two pieces of wood on a third placed transversely， so that their separation should be properly maintained.
that done， there was only the angle to calculate by bringing back the observation to the level of the sea， taking into consideration the depression of the horizon， which would necessitate measuring the height of the cliff. the value of this angle would give the height of alpha， and conse