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THE POPULAR SCIENCE MONTHLY 



clearly visible except when viewed at the 

 right angle. This property, however, has the 

 great advantage that it makes retouching of 

 the picture impossible. To remedy the in- 

 convenience arising from it, M. Lippmann 

 has devised an apparatus for viewing the 

 pictures by the aid of which the proper con- 

 ditions of the angle can always be obtained. 



Toads and Cancers. Toads were used 

 during the last century as local applications 

 for the cure of cancerous breasts. An ac- 

 count of a cure said to have been wrought 

 by this means is given in Martin's Natural 

 History, pubHshed in 1785, from a letter 

 from a physician to the Bishop of Carlisle. 

 The doctor had attended the operation for 

 eighteen or twenty days, and was surprised 

 at the result. The toad was put into a linen 

 bag, all but the head, and that was held to 

 the part. It was supposed to suck the poison 

 till it swelled up and died. Then other 

 toads were put on, and so, till the sore was 

 cured. Sometimes they disgorged, recov- 

 ered, and became lively again. Other au- 

 thorities, the writer said, held that the toads 

 did not suck the poison, although they ad- 

 mitted that the swelling and falling off dead 

 was a general consequence of the applica- 

 tion. Dr. Leonard G. Guthrie shows, in tlie 

 Lancet, that a toad can not suck, but when 

 injured or alarmed blows itself up to about 

 twice its ordinary size, and when held and 

 constrained for any length of time in a hot 

 hand, sweats profusely and would pi-obably 

 soon die. The efPect of the secretion when 

 held on the hand is to cause dryness, numb- 

 ness, and a tingling ; which it probably did 

 to the cancerous breast, giving a sort of re- 

 lief to the pain. 



A "Sanitary" Bnilding. Dr. W. Van 



der Heyden, of Yokohama, Japan, has de- 

 signed a sanitary building, in which he seeks 

 in winter to imprison the heat-rays of the 

 sun, and in summer to admit the light while 

 excluding the excess of heat; and at the 

 same time to afford perfect ventilation and 

 security against disease germs. The walls of 

 the houses are made of air-tight boxes with 

 sides formed of panes of glass, built upon 

 one another, hermetically jointed with felt, 

 and filled with a solution of alum ; the roof 

 is covered with cement. "A house built in 



such a way is an entirely closed hollow space, 

 like a box itself, without windows or doors 

 no openings, and no fissures. It is practically 

 impermeable to air, moisture, heat, cold, dust, 

 microbes, and insects." At convenient in- 

 tervals in the walls of rough plate glass are 

 plates of polished glass, to be used as win- 

 dows for looking out. "Doors are not 

 wanted, because the entrance can be made 

 through the floor by means of a lift or stair- 

 case from an underground room which re- 

 ceives no direct light from the sun. The 

 walls of the underground room are made of 

 ordinary bricks, plastered inside, and pro- 

 tected outside with a thick layer of clay to 

 keep out moisture ; it will be better to have 

 these walls constructed with iron plates, as 

 quick conduction of heat is the requisite 

 here. The light for this room comes through 

 glass boxes let in the four corners of its 

 ceiling which forms the floor of the upper 

 room. . . . There is a nice mild diffused 

 light in the lower room which fully enables 

 one to do any laboratory work, and is suffi- 

 cient to read by." The walls are protected 

 against freezing in winter by inclosing the 

 whole building in a covering of window glass. 

 In the summer the window-glass frames are 

 put within the house, and furnish air cush- 

 ions, still further preventing the accession of 

 outside heat. Special arrangements are made 

 for the renewal of air, heated in winter and 

 sterilized at all times ; and as the house is 

 proof against the entrance of air from any 

 other source, all microbes, disease germs, in- 

 fections, and insects are efficiently kept out. 

 The author has tried his house, and thinks 

 well of it. 



Temperature of the Interior of Trees. 



The experiments of M. Prinz on the varia- 

 tions of temperature in the interior of trees 

 seem to show that the sap contains large 

 quantities of gas, which escapes with a sound 

 often quite marked, and which can some- 

 times be heard two steps away. The mean 

 annual temperature of the interior of a tree 

 corresponds with that of the external air ; 

 but the monthly mean sometimes varies by 

 two or three degrees. It usually requires 

 about a day for a fluctuation of temperature 

 to be transmitted to the heart of a tree. 

 While the difference between the interior 

 temperature of a tree and that of the air is 



