At the moment a ship begins to move in a launching, the exact observation of her velocity, acceleration and starting force is of considerable importance in preparing future launching calculation, but to find an accurate launching acceleration seems quite a difficult problem and has not been, so far, radically treated.Investigating the results of various records of observation of actual launching, we can know the nature of the lubricant.The author, by means of a new method of directly recording the initial time-distance curve (the recording apparatus is shown in the photograph, Fig. 2), worked out the initial launching acceleration deduced therefrom ; and found, in some instances, a certain phenomenon of distortion appeared in the initial acceleration curve, this distortion is considered due to the effect of the resisting force caused by the trigger acting on the sliding way, after the former being once released. It is probable, unremoved bilge blocks, etc., might also cause the same effect.Figs. 3 and 4 give, as examples, the recorded initial time-distance curves at the actual launching of “a” and “b” ships.Figs. 5 and 6 show the ships' velocity and acceleration curves calculated.Fig. 7 is a part of another curve of acceleration recorded by an accelerometer, when “b” ship was launched, and to be compared with Fig. 6.Fig. 8 shows a probable schema showing the variation of mean frictional coefficient of the sliding surface at launching, as the author arrived at.