of Edinburgh, Session 1874 - 75 . 577 
like all human works, are not then perfect; they are so neither in 
the execution nor perhaps in the details of the conception; never- 
theless, they greatly surpass, not only in extent, but yet and above 
all in correctness, all the tables which have preceded them, as well 
as the more modern tables which have not been compared with 
them before publication.” 
The second paragraph, p. 12, of the pamphlet sent me, which on 
account of its length I do not quote, contains a capital error for 
which I cannot admit that I have given cause. Mr Sang says that 
there is a third copy of the tables which had been allowed to Prony 
by way of minutes. I have never said anything of the kind. 
There only exist, in fact, two manuscript copies of the Great 
Tables of the Cadastre. The introduction and notice which I 
have published in vol. 4 of the Annals of the Observatory leave 
no doubt on that subject. It may be seen therein how, after long- 
researches, I was led to discover that one of the two which was 
believed to have been lost. 
It is, therefore, unnecessary for me to seek to controvert the 
consequences which Mr Sang has drawn from the existence of an 
imaginary transcription. 
III. Mr Edward Sang, evidently led by the sole desire to obtain 
perfect logarithmic tables, would have the learned world to mistrust 
the Cadastre Tables. According to him, these afford no serious 
guarantee that the principle of the method was good, that these 
principles were faithfully carried out, or that the results were sin- 
cerely given. On these three heads Mr Sang uses me as a 
battering ram to demolish the edifice erected by Prony, and thinks 
he has so well succeeded that it was unnecessary to recapitulate 
the special criticisms which he had made. I think that he would 
have formed quite a different opinion if he had been privileged to 
spend years in the study of a work which fills nineteen folio volumes. 
In order to give an account of all the mathematical details of 
the method, it would be necessary to read Prony’s explanation in 
the (manuscript) volume forming the introduction to the tables. 
Although this memoir be not exceedingly voluminous, and although 
I have personally made a copy thereof, I have not found a printer 
willing to run the risk of the impression, and have, therefore, been 
confined to the honourable but restricted space kindly given by 
