While he was attending divine service in a winter morning, he had left in his study a favourite little dog called Diamond. Upon returning from chapel he found that it had overturned a lighted taper on his desk, which set fire to several papers on which he had recorded the results of some optical experiments. These papers are said to have contained the labours of many years, and it has been stated that when Mr. Newton perceived the magnitude of his loss, he exclaimed, “Oh, Diamond, Diamond, little do you know the mischief you have done me!” It is a curious circumstance that Newton never refers to the experiments which he is said to have lost on this occasion, and his nephew, Mr. Conduit, makes no allusion to the event itself. The distress, however which it occasioned is said to have been so deep as to affect even the powers of his understanding. This extraordinary effect was first communicated to the world in the Life of Newton by M. Biot, who received the following account of it from the celebrated M. Van Swinden. “There is among the manuscripts of the celebrated Huygens a small journal in folio, in which he used to note down different occurrences. It is side ζ, No. 8, p. 112, in the catalogue of the library of Leyden. The following extract is written by Huygens himself, with whose handwriting I am well acquainted, having had occasion to peruse several of his manuscripts and autograph letters. ‘_On the 29th May, 1694, M. Colin,[75] a Scotsman, informed me that eighteen months ago the illustrious geometer, Isaac Newton, had become insane, either in consequence of his too intense application to his studies, or from excessive grief at having lost, by fire, his chymical laboratory and several manuscripts. When he came to the Archbishop of Cambridge, he made some observations which indicated an alienation of mind. He was immediately taken care of by his friends, who confined him to his house and applied remedies, by means of which he had now so far recovered his health that he began to understand the Principia._’” Huygens mentioned this circumstance to Leibnitz, in a letter dated 8th June, 1694, to which Leibnitz replies in a letter dated the 23d, “I am very glad that I received information of the cure of Mr. Newton, at the same time that I first heard of his illness, which doubtless must have been very alarming. ‘It is to men like you and him, sir, that I wish a long life.’”