POPULAR MISCELLANY 



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the ramming was blown out. The machine 

 is described as very handy and compact, 

 and easily used, while the cost, beyond the 

 first outlay, is absolutely nil. 



The lleliotype Process. For some years 

 an eminent publishing-house in Boston has 

 been engaged in the production of " helio- 

 type " copies of famous works of art, and 

 the public is now more or less familiar with 

 the products of the " heliotype " process. 

 But what that process is we have nowhere 

 seen explained till recently a writer in the 

 Tribune gave a very intelligible account of 

 its modus operandi. In what follows we 

 propose to give in brief the main points of 

 the author's explanation : First a photo- 

 graphic negative is made in the ordinary 

 manner ; but the " positive " plate is peculiar. 

 The basis of its composition is gelatine, 

 with a mixture of bichromate of potash and 

 chrome alum. This mixture is dissolved in 

 hot water, and the solution is then poured 

 on a plate of glass or metal, and left to dry. 

 When dry it is about as thick as ordinary 

 parchment, and is stripped from the plate 

 and placed in contact with the previously- 

 prepared negative ; the two are then ex- 

 posed to the light. The bichromate of 

 potash makes the gelatine plate sensitive 

 to light, and wherever the light touches it 

 the plate becomes leathery or water-proof. 

 The result of the exposure to light is, there- 

 fore, that a portion of the gelatine plate 

 the image is water-proofed, while the re- 

 mainder is absorbent of water. Now, we 

 know what a repulsion exists between water 

 and greasy substances of every kind for 

 instance, printer's ink. It follows that, if 

 we moisten the gelatine plate, the unchanged 

 parts will absorb the water, and, if ink is 

 then rolled over it, it will adhere only in 

 the altered parts. By so applying ink, 

 the sheet of gelatine is converted into a 

 "positive" plate from which copies can 

 be taken on a printing-press. This plate, 

 strange to say, is very durable, and is capa- 

 ble of yielding, with fair treatment, several 

 thousand impressions. Of course, the sheet 

 of gelatine must have a solid base given to 

 it, to hold it firmly on the bed of the press 

 while printing. This is accomplished by 

 uniting it under water with a metallic plate, 

 exhausting the air between the two surfaces, 

 and attaching them by atmospheric pressure. 



Epidemics and Ablation. A short time 

 ago we published some remarks of Dr. He- 

 bra, of Vienna, depreciatory of the value of 

 frequent bathing. A diametrically opposite 

 opinion is held by the eminent hygienic 

 reformer, Edwin Chadwick, C. B., who cites 

 facts to prove that skin-cleanliness, cr in 

 other words frequent ablution of the whole 

 person, is a powerful preservative against 

 all infectious and contagious diseases. He 

 asserts that in children's institutions the 

 death-rate and cases of sickness have been 

 reduced one-third by regular head-to-foot 

 ablutions with tepid water. Experienced 

 trained nurses, regularly attending scarla- 

 tina-patients, give themselves regular head- 

 to-foot ablutions twice a day, and a change 

 of clothes once a day. Medical men of ex- 

 perience, who serve amid plagues and the 

 most terrible epidemics, do the like. Mr. 

 Chadwick adds: "If I had again to serve 

 as a member of a general board, and had 

 to exercise authority in providing defenses 

 against epidemics, I would propose regula- 

 tions for the immediate and general ' tub- 

 bing' of the population, and have it seen to 

 as sedulously as vaccination for protection 

 against small-pox." To show the influence 

 of skin -cleanliness on the assimilation of 

 food, Mr. Chadwick relates the following 

 incident: "A friend of mine," he writes, 

 "in command of a brigade in Spain, was 

 hemmed in, and his men were put on very 

 short rations ; and to amuse them it being 

 summer-time he encouraged them to bathe 

 daily in a river close by, and he marked, as 

 a result he had not expected, that his men 

 were in as good strength as the unwashed 

 soldiers on their full rations." Similar re- 

 sults are observable in the inmates of well- 

 kept prisons. 



New Process of Embalming. A new 



and inexpensive method of embalming has 

 been invented by Dr. Lowell, of Brook- 

 lyn. The preservative fluid he employs 

 is a solution of zinc chloride which is in- 

 jected into the body either by an artery or a 

 vein. The apparatus required consists of a 

 porcelain-lined vessel, which is elevated to 

 such a height that the solution may be in- 

 jected into the cadaver after the manner of 

 a gravity-syringe. For the passage of the 

 preservative fluid from this receptacle into 

 the vein of the cadaver, glass and rubber 



