Opera mechanica, geometrica, astronomica et miscellanea

The Opera Varia Various Works and the Opera reliqua Remaining Works encompass the writings of Huygenius Huygens completely, insofar as they were printed by Gravesande, as well as those in Leiden. In the year 1724, the Opera Varia came out in two volumes and contain exactly that which is contained in the fourth volume. Therefore, it is likely that only the title is new. The Opera reliqua came out in 1724. They contain the writings which were already in the Operibus posthumis posthumous works which were published by Volderus and Fullenius in the year 1703, and also the Tractatus de lumine Treatise on Light, the Dissertatio de causa gravitatis Dissertation on the Cause of Gravity, and, by Guido Grandi, the Geometrica demonstratio theorematum Hugenii autorum circa Geometric demonstration of the theorems of Huygens regarding Difference regarding the cause of gravity the Logarithmicam Lineam logarithmic line (these are 15 essays on the logarithmic line which Huygens had attached to his Word of Terms without proofs). As well as the Epistola geometrica ad virum Thomam Cevam S.J. non edita Unpublished geometric letter to Mr. Thomas Ceva, S.J.

In July of the year 1695, Joh. Bernoulli wrote to Leibniz (Commerc. epist. 1. tom. p. 61): "I understand from Holland that the noble Huygens is not indeed dead, but has been lying ill for a full four months; from France, however, it is written to me that he has fallen into a state of mental incapacity, which I heard some time ago was already reported to be true. I pray God that he may soon restore to that incomparable man the health of both mind and body." (Isacus Huygens was already truly dead as Leibniz was told in the following letter in Commerc. epist. p. 84): "You have undoubtedly understood that the incomparable Huygens has passed away. How great this loss is, one cannot say enough; because of the depth of his living judgment, combined with the greatest and most profound knowledge of things. I wish, as I hope, that there might be found among his papers things from which a part of the matters which he meditated upon might be brought to light for the public good. It is to be lamented that the strength of the illness, which had clouded his mind, did not permit him to decide and arrange for himself what would have seemed best to provide." Unless perhaps (as is wont to happen) he returned to himself shortly before his death and revealed his last will; if that has happened, it will not remain hidden for long.