CHARLES BABBAGE. 187 



same house, still interested in the calculating-machine, with apparently 

 but little diminution of mental activity. He informed me that he felt 

 himself gradually declining ; that he endeavored to note the change in 

 himself; that he found it difficult to enter upon new subjects of thought, 

 but that he could reason and mentally act on materials alreadj^ in his 

 mind in the way of new computations and new deductions. He regret- 

 ted the loss of memory, since with it was the loss of personal identity. — 

 J. H.] 



[Extract from writings of Charles Babbage.] 



OF OBSERVATIONS. 



There are several reflections connected with -the art of making obser- 

 vations and experiments, which may be conveniently arranged in this 

 chapter. 



Of Minute Precision. 



No person will deny that the highest degree of attainable accuracy is 

 an object to be desired, and it is generally found that the last advances 

 toward precision require a greater devotion of time, labor, and expense 

 than those which precede them. The first steps in the path of discov- 

 ery and the first approximate measures are those which add most to 

 the existing knowledge of mankind. 



The extreme accuracy required in some of our modern inqiiiiies has, 

 in some respects, had an unfortunate influence by favoring the opinion 

 that no experiments are valuable unless the measures are most minute 

 and the accordance among them most perfect. It may, perhaps, be of 

 some use to show that even with large instruments and most practiced 

 observers this is but rarely the case. The following extract is taken 

 from a representation made by the present astronomer-royal to the 

 council of the Royal Society, on the advantages to be derived from the 

 emplojTiient of two mural ckcles : 



'' That by observing, with two instruments, the same objects at the 

 same time, and in the same manner, we should be able to estimate how 

 much of that occasional discordance from the mean, which attends even 

 the most careful ohservations, ought to be attributed to irregularity of 

 refraction, and how much to the imperfections of instruments.^^ 



In confirmation of this may be adduced the opinion of the late M. 

 Delambre, which is the more important, from the statement it contains 

 relative to the necessity of publishing all the observations which have 

 been made : 



" Mais quelque soit le parti que I'on pr^f^re, il me semble qu'on doit 

 tout publier. Ces irregularit6s memes sont des faits qu'il importe de 

 connoitre. Les soins les plus attentifs n^en sauroient preserver les observa- 

 teurs les plus exerces, et celui qui ne produiroit que des angles toujours 

 parfaitement d'accord auroit ete singulierement bien servi par les circou- 

 stances ou ne seroit pas bien sincere." — Base de Systcme metriqtie^ dis- 

 cours preliminaire^ p. 158. 



