Transition Steadies 37
printed only in two colours, red outline for England and black shading for rain and cloudiness. It is entitled: "English Weather Data, Feb. 9, 1861, 9 h. a.m.," and is part of a circular issued from 42 Rutland Gate and dated June 12, 1861. "The accompanying sheet has been printed as an experiment, by means of movable types which I have had cast for meteorological purposes." To save confusion of figures, barometric heights were not inserted on the map, but lines of equal pressure having been deduced, the places where the isobars of each i of an inch cut the right- and left-hand borders of the map were marked, and a straight line joining any pair of corresponding figures was taken to be approximately the corresponding isobar. These isobars were not given on the map'.
In July 1861 Galton issued another circular, this time addressed to European meteorologists and printed in English, French and Germane. He appeals to them to provide synchronous meteorological data for a series of aerial charts of Northern Europe (latitudes, 42° 25' on the south, including all France and Perugia, to 61' on the north, including Shetland, Bergen and Christiania; from the westernmost limit of the British Isles to Konigsberg, Warsaw and Budapest). The data were to be for the whole month of
have survived. When the proper stamps have been attached the map is ready for photography or engraving. I do not know why Galton replaced these circular stamps by the oblong blocks of his later maps, possibly because the oblongs were easier to set up in a press and actually print on to the map. This map looks more graceful than those of the circulars, but contains somewhat less information. The two maps can be compared in the accompanying plates.
Specimens of Galton's circular stamps for attaching to maps and so forming synchronous weather charts. See footnote 3, p. 36.
' This circular almost in the same words appears as an article entitled "Meteorological Charts" in the Philosophical Magazine, Vol. xxii, 1861, pp. 34-5.
2 This is, I believe, Galton's first appeal by circular for the filling in of schedules, a practice considerably developed by him later.