402 Notes and Memoranda. 



Photographic Hints. — M. Civiale has obtained fine impressions by employ- 

 ing a mixture of one part of was and four of paraffine. Major Webster Gordon 

 employs equal parts of the iodide and bromide of cadmium in the preparation of 

 collodion for instantaneous photographs, -which he developes by means of pyro- 

 gallic acid. M. Keynaud remarks, that when great sensitiveness is required, the 

 collodion should contain but a very small quantity of free iodine. He also states 

 that bromide of silver is, in comparison with the iodide, more sensitive to the least 

 refrangible colours, red, yellow, etc. Bromides of ammonium and cadmium pos- 

 sess this property in a still higher degree. Bromide of potassium communicates 

 to collodion a delicacy similar to that produced by its iodide. For moist collodion 

 he employs three or four grammes of the bromide to twelve grammes of the iodide, 

 and one litre of normal collodion. 



New Chronograph. — Cosmos gives a brief account of an instrument invented 

 by Captain Schultz which is able to measure the duration of phenomena which 

 only last the five hundred thousandth of a second. It consists, first, of a drum, 

 about a metre in circumference, having its surface silvered and covered with lamp- 

 black before the experiment begins. A double motion gives this drum three turns 

 in a second. Its next portion is a " diapason" giving five hundred vibrations in 

 a second ; its third portion is a point fixed on the " diapason," which traces a 

 sinuous curve on the drum ; and lastly, it has a small electrical apparatus which 

 marks by an induction spark, the beginning and the end of the phenomenon, which 

 is investigated. " That which characterizes this instrument is the great length of 

 the mark on the cylinder which represents an infinitesimal duration;" and it is 

 affirmed that it recently measured the time occupied by a projectile fired from a 

 rifle in traversing a few centimetres. Each centimetre is equal to 0"3937 of an inch. 



Diatom Cysts. — Madame Liiders states the cysts enveloping certain speci- 

 mens of Goconema cistula, Gomphonema, etc., are not, as has been supposed, 

 vesicles formed by the diatoms, but Amoebae by whom they were assailed. 

 She found that an Amoeba occupied one or two hours in surrounding a group 

 of Synedra. This lady is also of opinion that observers have taken for spores 

 of diatoms small infusoria which are often developed in their interior. — Mold 

 JBotanische Zeitung, Bibliotlieqiie Universel, Feb. 1862. 



Leeches. — Dr. Ebrard observes that an adult leech gorged with blood re- 

 quires nearly eighteen months in a state of captivity for the process of digestion. 

 Young and free specimens accomplish the same task in six weeks or two months. 



Peculiar Greens. — In a recent paper on dyeing, read by Dr. Crace Calvert, 

 at the Society of Arts, he called attention to the curious fact that the greens pro- 

 duced by dyeing silks first with Prussian blue and then in an acidulated bath of 

 carboazotic or picric acid, appeared green in artificial light, while the greens ob- 

 tained with indigo and picric acid turned blue under the same conditions. He 

 also stated that the Chinese vegetable green Lokao, which M. Charwin has suc- 

 ceeded in obtaining from the Exnopean seed ffliamnus Catliarticus, is the only 

 substance he was acquainted with capable with suitable reagents of producing 

 the seven colours of the spectrum. 



Improvement in Kelp Manufactures. — Mr. Stanford dries the seaweed he 

 operates upon, and presses it into cakes, winch he carbonizes at a low red heat in 

 iron retorts, collecting the volatile products, among which he finds ammonia, wood 

 spirit, and paraffine oil. By this process a considerable loss of iodine is prevented, 

 and a larger quantity of useful products obtained. He hopes that the masses 

 of weed thrown up on the south coast of England will in future be utilized, espe- 

 cially as the deep water weeds from the Atlantic are found to be the most valuable. 



Development of Coral. — In No. II. Intellectual Observer, p. 167, we gave 

 a short account of the investigations of M. do Lacaze Duthiers on the growth of 

 coral ; we extract (he following additional particulars from Comptes Iioidus, 3rd 

 March, 1862. The embryos, which are vermiform, swim with their tails foremost 

 and mouths backwards, and after continually bumping against various objects, 

 liny fix themselves, and give op a locomotive life. They are most disposed to 

 come into contact with other bodies when their elongation ceases, and they begin 

 to lose the worm-like form. In their process of growth lliey become shorter and 



