Fred Pearson only assisted with the experiment. That is why is more commonly called the MGX. A later experiment was called MPX (Michelson, Pease, Pearson), 1929.
The quote is taken from an article written by Dr. P. Correa who is a fervent proponent of aether theory (his website is called aetherometry).
Now, the formula published by Michelson in 1925 (first presented in 1904) is actually the CORIOLIS EFFECT formula, not the SAGNAC EFFECT formula.
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1925ApJ....61..140M&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdfThe reason for the variations of the readings is very simple: the periodic effects depending upon the time of day of the ether drift.
This fact was a basic discovery of Dr. Dayton Miller:
http://www.orgonelab.org/miller.htmMichelson did not address the periodicity of the fringe shifts, instead he prudently offered this explanation:
In view of the difficulty of the observations, this must be taken to
mean that the observed and calculated shifts agree within the
limits of observational error.
However, Michelson did not record the TRUE SAGNAC EFFECT of rotation which for the latitude of Clearing, Illinois, is some 21,000 times greater than the CORIOLIS EFFECT recorded.
The periodicity of the ether drift was clearly recorded by Michelson, but not acknowledged.
Since the MGX did not record the SAGNAC EFFECT, and only the CORIOLIS EFFECT, this means that the experiment registered the effects of the ether drift upon the light beams.