28i
4 shows an idealised representation of this quasi-systematic effect,
in relation to the stability line 0O. The way the SHAR effect is
encountered in practice, is clearly illustrated in Figure 5 and the
consequences of being misled by a group of apparently stable
Schuler means is starkly evident in the curves which show the
Schuler mean variation superimposed by the SHAR trend in a
number of sample determinations. It will be seen from the five
examples cited that the range of the harmonic is of the order of
30" in many cases, less in others, and as high as 50" in one case.
