90 



POPULAR SCIENCE NEWS. 



[Jl'NK, 1889. 



countries certain of the colonies belonged. 

 A little later came the age of advertising cards, 

 and card-alluims were the universal rage. 

 A few of these are really artistic, and, if card 

 collecting shall foster a pure :csthetic taste, 

 we will not complain. In some localities, the 

 younger girls collect buttons, and display much 

 zeal and perseverance in hunting up new 

 varieties. We mention these only to show the 

 inherent passion with the voung for making 

 collections, and to suggest that it be turned 

 into some more promising channel. It is 

 here we would tempt the child to collect nat- 

 ural objects. There are probably few things 

 more attractive to the yoimg of both sexes 

 than butterflies, and, where these abound, a 

 pretty little collection is easily made. A col- 

 lection of insect&T— although it may be objected 

 that cruelty is involved in this — is also inter- 

 esting and instructive. The practice of col- 

 lecting birds' eggs we cannot approve of, 

 although we can afford to sacrifice one of our 

 feathery songsters, occasionally, if we know 

 that he is to pass at once into the hands of a 

 taxidermist, and henceforth be immortalized 

 in some scientific or amateur collection. 

 Another field open to all in spring and sum- 

 mer, is that of collecting and pressing flowers. 

 It is true, a herbarium is far inferior in beauty 

 to most other collections, and vet, properly 

 made and bound in books, it need not be so 

 repulsive as it generally is. A collection of 

 leaves alone, not selected for color and beauty 

 merely, but to exhibit all the varied shapes, 

 veinings, edges, etc., would be pretty and in- 

 structive. We hope some day to see leaf- 

 albums, similar to stamp-albums, with the 

 names of all the principal trees of our state, or 

 section, printed beneath the blank space 

 where the leaf itself is to be pasted. What 

 an incentive this would give the young collec- 

 tor to get all his blanks filled up, to know if 

 this was really the leaf that belonged there, 

 and to know something of >the tree on which 

 it grew. Exchanges would soon spring up, 

 and those leaves not found near home could 

 be obtained from other collectors at a dis- 

 tance. These are collections that can be 

 made by everyone and everywhere. On the 

 sea-shore, sea-weeds and salt-water plants, and 

 shells may be the objects sought. In many 

 localities, the collection and classification of 

 minerals is pleasant pastime, and to name and 

 label them correctly is exceedingly instruc- 

 tive. We know a printer in New York City 

 who has one of the largest and finest collec- 

 tions of Manhattan Island minerals extant, 

 and nearly all of them were collected by him- 

 self in strolls about the city before breakfast, 

 the balance of the day being occupied in his 

 business. 



In making collections of any sort, never 

 forget to carefully mark specimens at once, with 

 the locality where they were found. The 

 name may be added subsequently, as oppor- 



tunity oflers, and, in all cases, a scientific 

 arrangement is preferable to any other. 



In addition to making collections of flowers 

 and birds, those who have any skill with the 

 pencil should try to make copies on paper, 

 and thus acquire both taste and skill, which 

 shall give them much pleasure in after life, 

 filling many a lonely hour with pleasant pas- 

 time, and, beside, enabling them to more 

 thoroughly appreciate the beauties of nature. 



ANSWERS TO PUZZLES. 

 We have received numerous answers to the 

 scientific puzzles published in the May num- 

 ber, but no one succeeded in answering them 

 all correctly. The most correct list was re- 

 ceived from Charles C. Plitt, of Baltimore, 

 Md., who is therefore entitled to a year's 

 subscription. 



(i) This question was not, which is the 

 heaviest, a pound of feathers or a pound of 

 lead.'' but, which iveighs the most? Of 

 course, a pound is a pound, no matter of 

 what material, but, as all substances, when 

 weighed in the air, are buoyed up by a weight 

 equal to that of the amount of air they dis- 

 place, — just as a cork is buoyed up in the 

 water, — it is evident that an actual pound of 

 feathers, or any bulky material, will weigh 

 less than an actual pound of the denser lead. 

 If weighed in a vacuum, both would weigh 

 exactly alike. In certain scientific investiga- 

 tions, this small difference is an important 

 matter, and a correction must be made for it, 

 or, as is sometimes done, the balance is en- 

 closed in an air-tiglit case, and the weighings 

 made directly in a vaciunn. 



(2) The intensity of radiant heat is pro- 

 portional, not to the distance, but to the square 

 of the distance. Therefore, if the ice is re- 

 moved to twice the distance from the stove, it 

 will melt four times more slowly, or in forty 

 minutes. 



(3) In the polar regions the sun appears 

 to circle around the horizon in planes more 

 or less inclined to it. During the long mid- 

 summer day, the circles are entirely com- 

 pleted above the horizon, but, after the sum- 

 mer solstice, they gradually approach nearer 

 to it, till the Sim momentarily dips below it, 

 thus marking the end of the day. It immedi- 

 ately rises again, however, and completes 

 another circle in twenty-four hours, so that 

 the second longest day is twentv-four hours 

 long. After this, the days rapidly become 

 shorter, till, at the autumnal equinox, day 

 and night are of equal length, but, finally, 

 the sun remains entirely below the horizon, 

 for a varying period, depending upon the lat- 

 itude of the place of observation, giving a 

 night equal in length to the long day of mid- 

 summer. 



(4) As the light from the sun is constantly 

 passing to the earth, we really see it as soon 

 as it rises, notwithstanding the time taken by 



the light in its long journey. Any change 

 upon the sun's surface would not be visible to 

 us until eight minutes after it had happened, 

 but, at sunrise, we do not have to wait for the 

 light to reach us ; it is already at the horizon. 

 If this were not so, we should not see some of 

 the fixed stars until several years after they 

 had risen, which is a manifest absurdity. 



(5) As water is practically incompressible 

 at a pressure of one hundred pounds, no 

 water at all woidd escape from the boiler 

 when the safety \alve was opened. The 

 pressure would be relieved, but there would 

 be no expansion, as woidd occur in the case 

 of air, steam, or other compressible sub- 

 stances. 



(6) It is theoreticall}' impossible to com- 

 pletely exhaust the air from the receiver of 

 an air-])ump. Under a decreasing pressure, 

 air would expand indefinitely, and, no matter 

 how many strokes of the piston were made, 

 there would always be a little air left in the 

 receiver. The increasing vacuum would be 

 analogous to those mathematical cinves which 

 continually approach a given point, but can 

 never reach it. The most perfect vacuums 

 obtainable are produced 1)v chemical means, 

 but an absolute vacuum has probablv never 

 been obtaineil. 



(7) Water expands in freezing, and, con- 

 sequentlj', ice contracts in melting to an equal 

 degree. A little consideration will show that 

 this must be exactly equal to tiie voliune of 

 the ice which floats above the surface of the 

 water, and, therefore, the level of the water 

 in the vessel contaiifing the ice would not be 

 changed by its melting. 



(8) At first sight it would seem as if the 

 column of mercury in the barometer-tube 

 woidd be supported entireh h\- the air, and 

 woidd not aflect the weigiit exerted upon the 

 balance, but it must be rcmomliered that action 

 and reaction are always eciiial, and that the 

 upward pressme of the air upon tiie mercury 

 is balanced by an e<|ual downward pressure 

 upon the tube. Therefore, the total weight 

 indicated by the balance would be that of the 

 tube, plus the mercury contained in it, or 

 eleven pounds. 



[Spt'cial CorruspondeiK-e ot The Popular Science Neivs. ) 



PARIS lp:ttI':r. 



Amono the ni.-iny and varied scientific meetings 

 which will be held in Paris during; the course of the 

 exhibition, some are to be of a quite novel sort. 

 Such is the case, among others, with the future 

 meeting of the Colo'nihophiles, or the pigeon-breeders. 

 As the Colombophiles arc concerned onlj with 

 pigeons considered as instruments and carriers in 

 war-time, they have decided to hold their meeting 

 with the. aeronauts, who are engaged in a similar 

 pursuit. The meeting will beheld at the end of July, 

 and will be the occasion of interesting experiments, 

 among which are prominent the simultaneous as- 

 cension of a number of balloons, and the freeing 

 of a hundred thousand pigeons, — carriers, of 

 course, — which will tlj to their respective sta- 



