250 M.H. Fizeau on the Effect of the Motion of a Body 
that the result I have obtained is altogether free from this cause 
of error. : 
For the most part the observations were made with a velocity 
of 7:059 metres per second; in a certain number the velocity 
was 5°515 metres, and in others 3°7 metres. The magnitudes 
observed have been all reduced to the maximum velocity 7'059 
metres, and referred to the breadth of a band as unity, 
Displacements of the Differences between the 
bands for a mean velocity observed displacements 
of water equal to 7°059 and their mean value. 
metres per second, 
0200 1. » «© «© «) es 00380 
0220 1. 5 «6 « « » =OO010 
PAD it ent et, ohie ve se ODIOS 
O167 4. se we « +0068 
ONLY oh demon ace be O089 
0225 . « +s » » 0-005 
O47 ‘ » « +0017 
O225 © «© « 6 6 6 0005 
O2Z14 4 vos «oe ©) oS O016 
0230 sas : 0-000 
O24 a 5 ss, ee 
OR47 2 eos ss ©) +0017 
0224 . 6 «© ow ew 6 =0'006 
O8O7 «a we ewe +0077 
OB0F 6. sown #0077 
O°2B6 ie pes is eee t- 0086 
OAD ele lel eee: SRO 
0240 . « + » « » 4+0°010 
D189 cee tw wipe om O041 
Sum . 4373 
Mean . 0:23016 
By doubling the mean value we have 0°46, nearly half the 
breadth of a band, which represents the magnitude of the dis- 
placement produced by reversing the direction of the current in 
each tube. 
To show the deviations on each side, the differences between 
the several observed displacements and the mean value of all 
have been inserted in the Table. It will be scen that, in general, 
they represent a very small fraction of the breadth of a band; 
the greatest deviation does not exceed one-thirteenth of the 
breadth of a band. 
These differences are due to a difficulty which could not be 
overcome; the displacement remained at its maximum but fora 
very short period, so that the observations had to be made very: 
