In M. Davanne’s opinion this new invention of M. Garnier’s seems likely to have a useful and extended application.  The image may be made with powder of any desired color.  If it is on glass, it may be transferred to paper or other support by means of collodion or gelatine.  By employing enamel powders, this process gives a new method of producing vitrified images.  It may also be used as a simple method of reproducing engravings under certain circumstances; copies of diagrams, however intricate, could easily be produced on glass by it, and used for the illustration of lectures by means of the magic lantern.—­Photo.  News.

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DANGERS OF PYROGALLIC ACID.

By DR. T.L.  PHIPSON.

Some time ago, Dr. Napias, of Paris, who devotes much of his time to matters connected with hygiene, took up the subject of the hygiene of the photographer, and published in the Moniteur de la Photographie a series of papers which were afterward translated into English and published by Messrs. Piper & Carter, of London.  In them the worthy author has considered the action on the economy of the various poisonous substances which pass daily through the hands of our readers, and the best means of counteracting their influence.

Since then—­in fact, quite recently—­attention has been called in the medical journals to certain properties of pyrogallic acid which were perfectly unknown, and show that this substance, even when applied externally, may act as a violent poison causing death by its great affinity for oxygen.  I published a short note upon the subject in the Journal of Medicine, etc., for April last, and it may perhaps be useful to reproduce the facts here.  Physicians who were unacquainted with this energetic deoxidizing property of pyrogallic acid have proposed it as a substitute for chrysophanic acid in the treatment of skin diseases; but Dr. Neisser has made known a case of poisoning by an ointment of pyrogallic acid, which at once shows that considerable danger attends its use for this purpose.  A man of strong constitution was admitted into one of the wards of the Breslau Hospital to be treated for general psoriasis.  He appears to have been submitted to a kind of experimental treatment in order to test the curative properties of pyrogallic acid as compared with chrysarobine.  He was treated by friction with chrysarobine (in the form of a pomade of alcoholic extract of rhubarb, containing one-twentieth) on the one-half of the body, while the other half was treated in the same manner by a pomade containing ten per cent. of pyrogallic acid.  Six hours after the application the patient had violent shivering with vomiting and intense collapsus.  Death occurred on the fourth day.  Experiments were at once undertaken on rabbits, and proved that this catastrophe was due entirely to the pyrogallic acid pomade, and that the