g KANSAS ACADEMY OF SCIENCE. 



From this we learn that the diameter of a particle is about one 250,000,000th 

 of an inch, and therefore the number of particles in a cubic inch of air is not 

 far from 3 raised to the tenth power, or (to represent this number more ac- 

 curately to our comprehension) 3 with 20 ciphers annexed, thus: 300,000,000,- 

 000,000,000,000. Tait says that to get some understanding of it, we may say 

 that one of th;- particles that go to make up a drop of water is to the whole 

 drop as an ordinary base ball is to the whole size of the earth. 



Perhaps I car not better illustrate the extreme smallness of these par- 

 ticles than by dissolving a little of this coal-tar color known as fuchsin in 

 some water. In this carboy there are 10 gallons or about 40 liters of water. 

 I have weighed out, on a very delicate scale, four milligrams of this fuchsin. 

 That is one 10,000,000th of the weight of the water in the carboy. I dissolve 

 this dye stuff in alcohol for convenience and pour the solution into this 

 carboy of water. * You will notice the beautiful red or magenta color that 

 is produced, and you will see that the whole quantity of water is reddened. 

 This means that one part of the dye will color at least 10,000,000 parts of 

 water. How very small must the molecules or particles be. 



The chemical balance is the most important instrument that the analytical 

 chemist or the investigator uses. With it he weighs ponderable matter, 

 and the more accurate and the finer his weighings, the closer his results. 

 Much progress has been made in the construction of balances, so that now 

 the aluminum beam, the agate bearings and agate or steel knife edges, to 

 avoid friction as much as possible, and finally the short arm balance, to 

 facilitate rapid weighing, are common improvements to be found in every 

 laboratory. The balance is inclosed in a glass air-tight case to avoid the in- 

 accuracy that might be caused by draughts of air while weighing, and an 

 artificially dried atmosphere is always present, so as to avoid the errors 

 that might arise from excess of moisture. Moreover it is possible to pump 

 out the air from a balance case and weigh in a vacuum, as is done in many 

 of the finer physical and chemical investigations. 



For greater convenience the decimal system of weights is used, and we 

 say that we ordinarily weigh to the one-twentieth of a milligram. The 

 scales arc so delicate that they will fluctuate on the addition of a single hair 

 to the lead. 1 may illustrate this by balancing on the two pans of this 

 scale pieces of paper of the same weight. You can see by the spot of light 

 that is reflected on the wall from a mirror on the index that the beam is at 

 rest as the support is lowered, and the beam is free to move up and down. 

 The balance is then at equilibrium. Now I will write a name on this piece 

 of paper with a lead pencil and replace the paper upon the pan. You see 

 the result; the pan having the name written on the paper is heavier than the 

 other. That shows the weight of a great name. 



Dr. E. L. Nichols, a former president of this association, exhibited at the 

 Madison nieeting of the American Association for the Advancement of Sci- 

 ence, this summer, some photographs that he had taken of the intermittent 

 electric spark. Foi recording what takes place in infinitely small spaces of 

 time, ho makes use of the extreme sensibility of the photographic plate, and 

 he makes the assertion that there is thus far no exposure too short to be 

 recorded by it. By the use of this sensitive plate it is possible to photograph 

 the rifle buJlot at all stages of its passage through the air. It is possible 

 to observe the condensation of the air that takes place in front of the ad- 

 vancing bullet, and the waves showing the vacuum behind it. We can study 



