33 



A NEW SERIES OF SELF-RECORDING WEATHER INSTRUMENTS. 



^^S^lK^. 



THE 

 DAWSON- 

 LANDER 



'X^AX'ci - 



SUNSHINE 

 RECORDER. 



THE DAWSON-LANDER SUNSHINE RECORDER. 



Patent applied for. 

 As the name indicates, this instrument is designed to record actual sunshine, and not merely the 

 heat rays, or the ultra-violet or chemical rays emitted by the sun. If the sunlight is sufficiently strong 

 to cast a distinct shadow this instrument will record it. 



The specially-prepared charts are mada from silver chloride paper, which is perfectly stable and 

 uniform, quite unlike ferroprussiate paper. It is perfectly easy to ensure that all batches of silver 

 chloride paper are equally sensitive to light, thus absolute uniformity of the records is secured. This 

 recorder is an accurate scientific instrument, capable not only of recording all t\e actual bright sun- 

 shine, but showing every minute detail and the varving intensity of the sunlighr. It is thus a great 

 step in advance of the somewhat primitive appliance for burning a mark on a card, and thus giving 

 an approximate total amount of the J>righiest sunshine without regard to detail. 



Tbe instrument consists of a small outer cylinder of copper which revulves with the sun. and 

 through the side of which is cut a narrow slit to allow the sunlight to impinge on a strip of sensitive 

 paper, wound round a drum, which fits closely inside the other cylinder, but which is held by a pin so 

 that it cannot rotate. The paper being in direct contact with the aperture, no great accuracy is 

 necessary in setting the instrument, as the only thing affecting the record is the movement of the slit 

 independently of the paper. 



Diffused light is prevented from reaching the sensitive paper by means of a flattened funnel- 

 shaped hood fitted in front of the slit. 



The instrument is adapted for giving automatically a continuous rf cord for a week, a month, or 

 any required period. By means of a screw fixed to the lid of the outer cylinder the drum holding the 

 sensitive paper is made to travel endwise down the outer tube, an eighth of an inch daily, so that a 

 fresh portion of the sensitive surface is brought into position to receive the record. 

 The advantages of this recorder may be briefly summarised as follow: — 

 1st. — It is easily fixed and requires no delicate astronomical adjustment. 



2Dd. — Tha scale of the record does not vary from week to week, but is exactly half-aa-inch per 

 hour all the year through. No correction is needed for the equation of time ; the record (unlike that 

 from other instruments) gives the actual time that the sun was shining. 



;ird. — It gives a sharp and distinct record which can be easily read, being black on a white ground. 

 4th.— It registers for a day, a week, a month, or any required period, auto- 

 matically, being self-setting, although the record may be examined as desired. 



5th. — Being made throughout of C'pperand gun-metal, and being only four inches in diameter, 

 it is very compact, and durable. 



6th. — The price is less than that of other instruments in general use and the charts cost only afew 

 shillings a year. 



As it is essential for purposes of comparison that all sunshine recorders should register approxi- 

 mately the game amount ot sunshine, the narrow slit in this instrument has for the present been 

 reduced from l-30th of an inch to l-10<_Hh of an inch, so that it registers the same amount of sunshine 

 as the Campbell-Stokea recorder ; but it is not generally known that the glass ball of the latter in- 

 strument frequently turns yellow on continued exposure to the sun. and this gradually reduces tbr 

 amount of sunshine that it registers. If a Campbell-Stokes record is ph"tographed, the photograph 

 will frequently' show much more sunshine than the original record, faint sunshine barely visible to 

 the naked eye comes out quite plainly in the photograph. 



