FROM ORDINARY DAYS OF THE ELEVEN YEARS 1890 TO 1900. 
229 
§ 13. Fig. 11 shows vector diagrams in two vertical planes. The upper six curves 
refer to the vertical plane through the geographical west, the lower six to the 
vertical plane through geographical north. The upper three WY curves and the 
upper three NV curves represent the mean diurnal inequalities for the three seasons 
derived from the whole eleven years. The three lower diagrams in each case 
represent the mean diurnal inequality for the year, derived respectively from the 
sunspot minimum group of years, the whole eleven years and the sunspot maximum 
group of years. The origin of co-ordinates is marked in each case by a small cross. 
The two large crosses show the orientation, one for the WY diagrams, the other for 
the NV diagrams ; the arms of these crosses each represent 10y. It will be noticed 
that Y is measured positively downwards in both cases. 
The three WY diagrams for the year differ markedly in amplitude, but 
comparatively little in type, closely resembling the equinoctial diagram from the 
eleven years. The special feature is the beak occurring about 8 a.m. This beak is 
also prominent in the summer diagram, occurring, however, nearly an hour earlier. 
Associated with the beak is an indentation or bay, extending from about 6 p.m. to 
7 or 8 a.m. In the summer diagram the curvature is small near the deepest part of 
the bay, and except at the beak is large only from 6 to 8 p.m. In the diagrams for 
equinox and the year there is, as it were, a pushing forward of the shore line of the 
bay from 6 p.m. to midnight, leading to a marked indentation in the early morning 
hours. This advance of the shore line of the bay in the afternoon hours has so far 
developed in the winter diagram that all that remains of the bay is the very 
deep narrow indentation in the early morning hours. The beak is still represented 
in the winter diagram at 9 a.m., i.e., about an hour later than in the equinoctial 
diagram, and two hours later than in the summer diagram, but it is now over¬ 
shadowed by the protuberance near midnight. 
The three NY diagrams for the whole year again differ mainly in amplitude. 
They all show a distinct loop near mid-day, somewhat more developed relatively in 
the sunspot minimum diagram than in the other two. The sunspot maximum and 
eleven-year diagrams show also a very small loop near 4 a.m. In the sunspot 
minimum diagram this is represented by a sort of tail, with its tip at 5 a.m. The 
hour marks for several hours on end are so nearly on a straight line, that it is 
impossible to say whether there is a true loop, as in the eleven-year diagram, or a 
very narrow indentation. The equinoctial diagram very closely resembles that for 
the eleven years. The summer diagram shows a considerably larger development of 
the mid-day loop, but the early morning loop has disappeared and is represented by a 
small tooth. The winter diagram shows development in an opposite direction. The 
mid-day loop has disappeared, and instead of a loop in the early morning there is 
a long narrow promontory, which like the rest of the diagram is described anti¬ 
clockwise. 
A feature in NV diagrams to which attention was called some years ago by 
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