146 Chronicles of Science. [Jan., 



experiments on the blue of the sky and the morning and evening 

 red, pure mastic is dissolved in alcohol, and then dropped into 

 water well stirred. When the proportion of mastic to alcohol is 

 correct, the resin is j)recipitated so finely as to elude the highest 

 microscopic power. By reflected light such a medium appears 

 bluish, by transmitted liglit yellowish ; wliich latter colour, by aug- 

 menting the quantity of the precipitate, can be caused to pass into 

 orange or red; but the development of colour in the attenuated 

 nitrite-of-amyl vaj)our, though admitting of the same explanation, 

 is doubtless more similar to what takes place in our atmosphere. 

 The blue, moreover, is purer and more sky-like than that obtained 

 from Briicke's turbid medium. 



Space will not admit of our referring to the experiments made 

 on iodide of allyl, iodide of isopropyl, hydrobromic acid, or hydro- 

 chloric acid ; but the results obtained with hydriodic acid are of so- 

 startling and unprecedented a character that we consider it im- 

 portant to give them in Professor Tyndall's own words, as follows : 

 " I have seen nothing so astonishing as the effect obtained on the 

 28th of October with hydriochc acid. The cloud extended for 

 about 18 inches along the tube, and gradually shifted its position 

 from the end nearest the lamp to the most distant end. The 

 portion quitted by the cloud proper was fiUed by an amorphous 

 haze, the decomposition which was progressing lower down being 

 here apparently complete. A sjDectral coue turned its apex towards 

 the distant end of the tube, and from its circular base filmy 

 drapery seemed to fall. Placed on the base of the cone was an 

 exquisite vase, from the interior of which sprang another vase of 

 similar shape ; over the edges of these vases fell the faintest clouds, 

 resemblmg spectral sheets of liquid. From the centre of the upper 

 vase a straight cord of cloud passed for some distance along the axis 

 of the experimental tube, and at each side of this cord two involved 

 and highly iridescent vortices were generated. The frontal portion 

 of the cloud, which the cord penetrated, assiuned in succession the 

 forms of roses, tulips, and sunflowers. It also passed through 

 the appearance of a series of beautifully shaped bottles placed one 

 within the other. Once it presented the shape of a fish, with eyes, 

 gills, and feelers. The light was suspended for several minutes, and 

 the tube and its cloud permitted to remain undisturbed in darkness. 

 On reigniting the lamp, the cloud was seen apparently motionless 

 witliin the tube ; much of its colour had gone, but its beauty of form 

 was unimpaired. Many of its parts were calculated to remind one 

 of Gassiot's discharges ; but in complexity and, indeed, in beauty, 

 the discharges would not bear comparison with these arrangements 

 of cloud. A fiiend to whom I showed the cloud, likened it to one 

 of those j(.'Uy-like marme organisms, which a film l)arely cai)able of 

 reflecting the hght renders visible. Indeed no other comparison is 



