Jacques Wardlaw Redway

“ Irrigated lands, however, produce crops that are extraordinary in quantity and unsurpassed in quality. The Lake region is below the average in sunshine, but the deficiency does not impair the quality of the fruit crop. The region of greatest cotton production receives from 60 to 70 per cent; and a comparison of this region with that of a lower per cent shows that the higher per cent is essential. Practically every part of the United States receives enough sunshine for a fair crop production, and a very great part receives enough for maximum production. ”

“ Even with recording instruments having the best possible adjustments, the record of sunshine for a given period is an approximate only; there is no such refinement in sunshine measurements as exists in measurements of pressure or of temperature. ”

“ The expansion of a volume of air in a blackened tube pushes a column of mercury between two platinum points, the ends of which pierce the tube, thereby making an electric circuit possible in the recording apparatus. The air volume within the blackened tube is exceeding sensitive to heat. Even in the coldest weather, the heat of direct sunshine is sufficient to push the mercury to the circuit-making points; with the absence of sunshine the mercury drops below them. Inclining the tube takes some of the weight off the air chamber and causes the mercury to be more easily lifted. ”

“ When the sun is shining, a contact of the clock completes the circuit. The movement of the armature operates a jigger, which moves the pen once every minute. The jigger and the progressive movement of the drum cause the pen to make steps in series of five, back and forth. Each series represents five minutes of time. These continue while the sun is shining. When the sun is not shining, the mercury in the thermometer drops away from the platinum circuit points. ”

“ In the latitude of New Orleans, June days are about 14 hours long; in the latitude of Minneapolis they are nearly 16 hours. The aggregate warmth is about the same in each case. The oblique rays of the sun and their lower heating power are balanced by greater duration in time. ”

“ The registering paper gives the best record, on the whole, when set at the focus of greatest light intensity. The best focal distance cannot always be determined by rule of thumb, however; it varies slightly with the locality, and therefore the optimum focal distance must be determined by the observer.
Sunshine in the United States. Figures show the per cent of possible sunshine.
order to overcome the friction of the mercury against the glass, it is lubricated with alcohol. The upper part of the tube, which is not blackened, also contains air. ”