302 Natural-Philosophical Collections. 



inches fell, and a SW. gale from over the Atlantic blew strong two days before 

 and two days after the last new moon, which in connection with this depth of 

 rain, must have caused the swell and comparative difference in the last spring tides 

 on our shores. A remarkably low ebbing of the tide, six feet lower than is us- 

 ual at the same age of the moon, occurred here the third day after the new moon 

 in March — Ibid. 



On the Formation of Formic Acid.—lSil. C, G. Gmelin has prepared formic 

 acid from cane sugar, sugar of milk, starch, wood, the root of the althcea, 

 mucic acid, &c. by distilling those bodies with dilute sulphuric acid and pe- 

 roxide of manganese ; but the formic acid thus obtained is always impure. He 

 has, however, obtained it in a high state of purity, by distilling alcohol with sul- 

 phuric acid and oxide of manganese. But to prevent the formation of ether, dilute 

 alcohol must always be employed ; common spirits of wine is the most conveni- 

 ent. Concentrated alcohol produces not only sulphuric ether, but also formic 

 ether. 



M. Gmelin has not been able to prepare formic acid by the use of acetic acid. 



The fibrin of the blood furnishes a very impure formic acid Annalen der 



Physik. und Chemie. xvi. 55. 



On Artificial Crystals of Oxide of Iran. — M. Mitscherlich has examined 

 crystals of oxide of iron, found in a pottery furnace at Oranienbourg. They 

 were in very obtuse rhomboids, and resembled the specular iron of volca., 

 noes, having the same brilliancy, hardness, streak, and other properties. The 

 smaller crystals, composing extremely thin plates, were transparent and red, like' 

 micaceous iron. The faces were brilliant, the angles could be measured, and. 

 were the same with those of the natural crystaL So greatly do these resemble^ 

 the crystals from volcanoes, that the same theory of formation may be applied to. 

 both. The first are formed in a pottery furnace, in which the vessels, when 

 baked, are glazed by means of common salt. The clay used consists principally; 

 of silica, alumina, and a litfle oxide of iron. The salt is volatilized, and 

 water coming in contact with the surface of the vessels, new compounds are pro- 

 duced, the water is decomposed, muriatic acid is formed, and the soda produced . 

 unites with the silica to make the necessary glass. As to the oxide of iron, its 

 history will be best understood by an experiment or two. If a mixture of salt, 

 oxide of iron, and silica, be heated to redness in a tube, and water in vapour be 

 passed over it, much muriatic acid is formed, but very little chloride of iron, and 

 crystallized oxide of iron will be found in the mass : but if muriatic acid be 

 brought in contact with ignited oxide of iron, water and chloride of iron are form- 

 ed, and sublime ; if the chloride of iron come in contact with more water, muria- 

 tic acid is first developed, then chloride of iron, and a residue of crystallized ox- 

 ide of iron remains. The formation of chloride of iron by the action of muriatic 

 Hcid upon oxide of iron appears, therefore, to depend upon the proportion of wa- 

 ter present. M. Mitscherlich applies these experiments and principles in explan- 

 ation of the manner in which volcanic crystallized oxide of iron is formed — all the 

 conditions necessary, according to the above view, being present in those cases, 

 where heretofore it had been supposed the oxide of iron, as such, had been actu- 

 ally sublimed — Bull. Univ. B. xix. 245. 



Account of a curious phenomenon of revolving motions, produced by the com- 

 bination of Alcohol with Laurel Oil. By Dr. Hakcock -To exhibit a singu- 

 lar spectacle which seems to bear some analogy with the motions of the planetary 

 orbs, take a vial of laurel oil and drop into it, at different intervals, some 

 rectified spirits of wine, when the most interesting results will be observed to 

 ensue ; a circulation presently commencing, of globules of alcohol up and down 

 through the oil, which will last for many hours, or for days, (how long is un-. 



