1^6 PHILOSOPHICAL TRANSACTION'S. [aNNO I674. 



Brasilian observations, on the 5th of March 1668 (N. S.), at 7 o'clock at night, 

 Father Estancel began to see this comet a little above the horizon, from west 

 to east-south-east. At the very beginning it appeared in its greatest bulk, and 

 with extraordinary brightness, whereas usually they at first appear small, and 

 then gradually increase. The beginning of its tail was a little under the two 

 lucid stars, the 15th and l6th, of the Whale's back, over which it then passed, 

 the whole length being about 23 degrees. The globe or head of it was so small 

 and thin, that very few could discern it with the naked eye; and the father 

 needed a telescope to see it well. The 7th of March, the former brightness 

 was somewhat less, and become so thin, that the eye could easily see the stars 

 that were behind it. The 8th, there were discovered more fixed stars behind 

 the Chevelure ; from the 8th, 10th and llth day, until it came to the little 

 Hare and to Eridanus, certain small stars, being in that celestial river, likewise 

 appeared through it. The tail was always directly opposite to the sun. As to 

 the colour of this comet, it was at first very splendid, and its rays v^^ere reflected 

 from the sea to the shore, where the observers stood. But this brightness lasted 

 only for three days, after which it considerably decreased. But what seemed 

 remarkable was, that having lost so much of its light, yet its bulk was not 

 diminished, but continued rather increasing till the comet disappeared. 



Directions for Tanning Leather* according to the New Invention of the Hon. 

 Charles Howard of Norfolk ; and a Machine for heating and cuttirig the Mate- 

 rials. N'' 105, p. 93. 



Every part of the oak-tree, of what age or growth it may be, and all oaken 

 copice w^ood, of any age or size, being cut and procured in barking time, will 



* In the tanning of leatlier, some improvements were suggested by Dr. Macbride several years 

 ago, (Phil. Trans. Vol. 68). This process has been further elucidated by modern chymists, and par- 

 ticularly by Mons. Seguinj and it now appears tliat the changes produced on hides, in the operation 

 of tanning, are owing to the combination of a peculiar substance, called tannin, (present in oak- bark, 

 galls, &c.) with tlie glue or gelatine of the skin. It has been supposed by the French chymist 

 abovementioned, that the gallic acid (also present in those astringent vegetable substances), has con- 

 siderable influence in promoting this process ; but from the recent experiments of Mr. Davy, (Phil. 

 Trans, for the present year, 1803), it may be inferred that this is not the case. One object which 

 Mr, -Davy proposed to himself in his experiments was to ascertain, what indeed had been before 

 attempted by Mr. Biggin, (Phil. Trans, for 1799)> in the case of the several barks used by tanners, 

 the relative quantity of tannin in certain astringent vegetable substances j and tlie result shows, that 

 catechu or terra japonica, contains this pi^inciple in the largest proportion. It would appear, that lib 

 of catechu is, for the purpose of tanners, equal to 7 or 8 lbs. of oak-bark. As connected with this 

 subject, we would furtlier refer the reader to Mr. Davy's observations on the preparation of skins for 

 tanning, inserted in the 15th Number of the Journals of the Royal Institution, for the present year 

 1803. 



