Figure 1 6. — Richard's registering aneroid barometer, an instrument used at 

 the U.S. Weather Bureau about 1888. The Richard registering thermoineter 

 is similar, the aneroid being replaced by an alcohol-filled Bourdon tube. 

 {USNM 2^2g8i; Smithsonian photo ^Sy^p-C^ 



late 19th century instruments can only be tentatively 

 drawn. The conclusion is inescapable, however, that 

 the majority of the instruments upon which the self- 

 registering systems of the late 19th century were based 

 had been proposed and, in most cases, actually con- 

 structed in the 17th century. It is also evident that 

 in the 17th century at least one attempt was made at 

 a system as comprehensive as any accomplished in the 

 19th century. 



To attribute the success of self-registering instru- 

 ments in the late 19th century to the unquestionable 

 improvements in the techniques of the instrument- 

 maker is to beg the question, for it is by no means 

 clear that the techniques of the 17th-century instru- 

 ment-maker were unequal to the task. It should also 



be noted that the photographic and electromagnetic 

 systems of the 19th century seem to have been some- 

 thing of an interlude, for some of the latest and most 

 durable (all of Draper's and Richard's instruments 

 and Marvin's barograph) were purely mechanical 

 instruments, as had been those of Hooke and Wren. 

 If we conclude that the 19th-century instruments 

 were more accurate, we should also recall Forbes' 

 comments upon the question of instrumental accuracy. 

 What, then, was the essential difference between 

 the 17th and 19th centuries that made possible the 

 development of the self-registering observatory? It 

 would appear to have been a difference of degree — 

 the maturation in the 19th century of certain features 



PAPER 23: THE INTRODUCTION OF SELF-REGISTERING METEOROLOGICAL INSTRUMENTS 



115 



