y20 KANSAS CITY REVIEW OF SCIENCE. 



In order to use a cement successfully we must know to what class it belongs 

 and treat it accordingly. Next, we must know how to put it on. lu no case 

 should it be used in a large quantity. The less the better is a good rule to 

 follow. 



In mortar we mingle sand, which makes the actual thickness of the lime be- 

 tween the stony surfaces in all cases very slight, however much mortar we may 

 employ. In the use of glue this is not practiced or necessary. The joints made 

 by carpenters are good examples of the minute quantity of a cement which is 

 necessary. Place a well-made glued joint on the edge, and it is almost impossi- 

 ble to find the lines of glue. Its position is mainly discovered by the direction 

 of the grain of the wood. 



Intimate contact between the cement and edges is necessary. This is not easy, 

 on account of the layer of air which adheres to all bodies. This layer of air is 

 what causes needles to float when carefully placed upon the surface of water. 

 When an object is warmed the film of air is easily moved, the hot needle sinks, 

 and to the hot body the cement will adhere easily. It is faulty for this reason, 

 that in gluing it is needful to have the work warmed. The rubbing of the sur- 

 faces together gets rid of the air, and then not only with glue, but with all ce- 

 ments, the surfaces must be pressed closely together. 



Common glue has most enormous strength and adhesive powers if it is good. 

 But to be good it must not have been injured in the making by decomposition, 

 to which the material and the glue itself are peculiarly subject. Here the lectur- 

 er detailed at some, length the process of glue-making, and said that if glue was 

 not pleasant to both taste and smell, it would not be strong. If not offensive, it 

 could be trusted to hold wood more strongly than its own fibers. 



The strongest known glue is that made from the skins and sounds of fishes, 

 and the strongest of this class is made in Lapland, from the skin of a perch. 

 The Laplanders use it in making their bows, which are both strong and durable. 

 In making it their cold cHmate is greatly in their favor ; here a fish skin will begin 

 to undergo decomposition before it can be dried. 



In making it the skins are put into a bladder, which answers for a water 

 bath, and heated in water until a sort of glue results. This glue is, as may be 

 imagined, very elastic. Isinglass is a very strong glue, made from skins, sounds, 

 etc., of fishes; it is very liable to be spoiled in making by overheating. 



BOOK NOTICES. 



The State and Higher Education. An address before the Minnesota Acad- 

 emy of Natural Sciences, by Prof. N.' H. Winchell. 



The address takes the ground that the State "should not only take measures 

 to qualify her citizens to read their ballots, but to discharge all the duties of high 

 citizenship." 



