576 Proceedings of the Royal Society 
the less likely since Vlacq, the author of these valuable tables, 
had been a printer, and was the immediate predecessor of Petrus 
Rammasenius. 
I willingly admit that, in the course of successive impressions, 
the copies of Vlacq may have been made more correct ; it is thus 
possible that a particular copy may not contain precisely all the 
errors indicated by Vlacq, Vega, and other authors, among whom 
I may count myself. But what danger is there from that? there 
are fewer corrections to be made ; that is all. 
I admit that it is not always very easy to procure a copy of the 
u Arithmetica Logarithmica” of Vlacq, and that the scarcity of the 
book enhances its price. However, the want may be advantageously 
supplied by the Thesaurus Logarithmorum Completus of Vega, 
a most estimable work, not so rare and therefore not so costly as 
the other. I subjoin a copy of a list of errors in Vega which I 
have made, and of which I willingly authorise the publication ; 
my copy of the Thesaurus has the legend Leipzig, 1794. 
There can be no serious difficulty in consulting the 4th volume 
of the (i Annales de l’Observatoire de Paris,” in such towns as 
Edinburgh, London, etc., where there are public libraries and 
scientific establishments of the first order. The copying of my 
errata is the matter of a few hours. 
II. I come now to the Great Tables of the Cadastre, on which 
subject chiefly I find it necessary to rectify several of Mr Sang’s 
interpretations. 
The observations made by M. Le Verrier at the meeting of the 
Academy of Sciences of Paris, of date 17th May 1858, were not 
the results of a personal examination made by the Director of the 
Observatory, but of the conferences which I had the honour of 
having had with him. As I have said in the note presented at the 
Meeting of the 24th May: — “ M. Le Verrier has been kind enongh, 
at the previous meeting, to mention my researches.” Hence the 
doubts expressed by this philosopher as to the true originality of 
the calculations in some places, have neither more nor less weight 
than those which I myself have expressed at this meeting of the 
24th May, and do not weaken in the least the conclusion which I 
maintain more firmly than ever: — “The Tables of the Cadastre, 
