74 



THE LANCASTER FARMER. 



[May, 



if they would take the trouble to notice the 

 coast of our own bay during a full tidi-; they 

 would find that the bushes and marshes for 

 several feet above tlie coast line are submerg- 

 ed in water. Now it is au acknowledged fact 

 that crabs, when being divested of their outer 

 shells, seek abiding place in tall grass, bushes 

 and marshes, away from their natural enemy, 

 sword-fish, hard-shell crabs, etc. May it not 

 then have been ordained by an All-wise Prov- 

 idence that these crustacean delicacies should 

 shed their shells at a period when the tide 

 and the grasses conspire to aid them in their 

 march after a safe hiding place ? If so, this 

 idea of the fishermen is, after all, not so ab- 

 surd. Crabs, like insects, shed their shell.s in 

 a singular manner. It is not easy for a crab 

 to squeeze its muscles, segments, etc. through 

 its sternum. A happy expedient, therefore, 

 has been hit^ upon by nature for eilecting a 

 shedding of shell. A crab in shedding drives 

 the blood from its lower portion by a natural 

 process into its claws, fins, etc. Then the 

 muscles of its lower portions being contracted 

 and thereby decreased in size, it is pulled 

 through the sternum. After being freed the 

 blood is again driven b.ack to the freed mus- 

 cles and those confined being contracted are 

 liberated in turn. A claw taken from a crab, 

 it matters not at what joint, is nearly always 

 replaced by a second growth. The hermit 

 crab is a crustacean, much smaller than the 

 edible crab, which inhabits a snail shell. This 

 crab enters a shell, and if it be filled with 

 dirt, it cleans it out; if inhabited by a smaller 

 hermit crab it cleans it out also [laughter;] 

 and if held by an enemy superior to it in 

 valor, it gets cleaned out itself. [Laughter.] 

 It seems to be the natural tendency of this 

 animal to be always looking for a new shell. 

 Its claws protrude from the shell from place 

 to place. If it be travelling alon^ in the 

 water and it sees another shell, it seizes it at 

 once and proceeds to inspect it. He enters it, 

 and if occupied the pantomime, as before de- 

 scribed is enacted, if not he takes possession, 

 and proceeds to see whether it will suit him 

 or not. He carries on a comparative inspec- 

 tion, goes from the new shell to his own to 

 see which he likes best, gets out of the new 

 one and lets it drop in the water to test it 

 before making the exchange. 



FARMERS' 



RETURNS TO CENSUS 

 TAKERS. 



The farmers must look out for the census 

 taker, who will begin his round on the first of 

 next June, and must complete them within 

 the month. The returns required of them 

 will of course be for the year 1879, for the 

 cereals, beans, peas, rice, tobacco, cotton, 

 fruits of all kinds, hay, clover, grass-seed, 

 hemp, flax, lioney, sugar-cane, sorghum, and, 

 in short, everything harvested in the fall. 

 The returns fdr the portion of 1880 will in- 

 clude mai)le-sugar and molasses, and wool 

 clipped chielly in the spring, except in South- 

 ern California, Texas and some of the other 

 Southern States, where two clippings a year 

 are obtained. For certain agricultural pro- 

 ducts there is no regular harvest, for they are 

 gathered as they mature, week by week, and 

 day by day. These comprise butter, cheese, 

 milk sold, value of animals slaughtered, yield 

 of market gardens, timber of all kinds and 

 home manufactures. The returns must be 

 made as accurate as possible, but will be very 

 little labor to the careful farmer. 



INFORMATION FOR ALL WHO 

 BREATHE. 



If there is any one thing that the average 

 amateur ventilator is more sure of than 

 another, it is that carbonic acid gas is the 

 principel evil to be guarded against. 



When he writes his first paper on the sub- 

 ject, he will enlarge upon tlie "deadly nature 

 of this subtle poison," and will refer to the 

 Black Hole of Calcutta as proving its powers. 

 He will also in the same paper announce his 

 discovery that "this deadly gas is heavy and 

 collects near the floor," and that, therefore, 

 special arrangements shonld be made to re- 



move it from that point. He may also in- 

 dulge in some speculations as to the well- 

 known great mortality among children under 

 five years of age being due to the fact that 

 they are so short, that their faces are con- 

 stantly bathed in this pool of heavy gas, and 

 he will allude in a familiar manner to the 

 Grotto del Cane. 



It he happens to be an architect he may 

 even proceed to put his theory to a practical 

 test, for I have seen, in two large and costly 

 buildings, holes carefully provided at the 

 level of the floor to allow this terrible car- 

 bonic acid gas to run ort". 



Now, all this is nonsense ; and until you 

 know enough of the physics of gases in general, 

 and of carbonic acid gas in particular, to be 

 sure that it is nonsense, and to be able to 

 demonstrate why it is so, it is useless to dis- 

 cuss ventilation problems with 5'ou. Let us 

 assume that what little you ever knew about 

 this subject you have forgotten, and then 

 note a few of the characteristics of gases in 

 particular. 



The Great Air-Ocean We Live In. 



Tlie atmosphere which surrounds us like 

 an ocean, at the bottom of which yon are to 

 construct your buildings, is compoised of three 

 gases, viz.: oxygen, nitrogen and carbonic 

 acid. These gases are mixed in varying pro- 

 portions, the amount of carbonic acid being 

 very small. The mixture is a very perfect 

 one, although these gases have each a differ- 

 ent weight for the same bulk, and this uni- 

 formity of mixture depends upon what is 

 known as the law of the diffusion of gases. 

 Every gas expands freely and rapidly into a 

 space occupied by another gas, much as if 

 this space were a vacuum. If you take a tall 

 glass jar and introduce at the bottom some 

 pure carbonic acid gas, leaving ordinary at- 

 mosphere air above, and close the jar, you 

 will find in a short time that the carbonic 

 acid has diffused upwards and the air down- 

 wards, until the composition of the mixture 

 is exactly the same in all parts. Observe, 

 also, that this mixture will never separate 

 again, unless you compel such separation by 

 placing in it some substance which will com- 

 bine with or absorb one of the gases and not 

 the others. 



In our ocean of air, the proportion of car- 

 bonic acid to the other gases is the same at a 

 point ten miles above the earth as it is on the 

 sea level, just as the proportion of salt in the 

 ocean is the same at one foot below the sur- 

 face as it is at one mile depth. 



The same is the case with an inhabited 

 room ; the proportion of carbonic acid at the 

 floor will be about the same, and in some 

 cases less, than at the ceiling, depending upon 

 the currents in the room, and upon the fact 

 that the principel sources by which the pro- 

 portion of this gas is increased in a room, 

 viz. : respiration and lights produce it usually 

 in a mixture at a higher temperature than 

 that of the room, and weighing less than the 

 same bulk of ordinary air. For this reason it 

 rises ; and by the time it has cooled it is 

 thoroughly difl'used through and mixed with 

 the rest of the air of the room, from which, as 

 just explained, it will not separate. 



The Only Exception to the General Rule. 



If carbonic acid is produced rapidly in a 

 space enclosed on all sides except at the top — 

 as for instance in a well or shaft of a mine, or 

 in a large empty beer or wine vat — it will ex- 

 pel the air and remain at the bottom of the 

 space until diffusion has been accomplished. 

 When in such a case the temperature of the 

 carbonic acid gas is the same as that of the 

 surrounding air, so that no currents are pro- 

 duced, the process of the diffusion is slow; 

 and if a slight production of carbonic acid gas 

 be kept up from below, it will remain almost 

 like water in a barrel, as it does in the 

 Grotto del Cane and in the places above re- 

 ferred to. It is only under such circumstances 

 however, that it is ever necessary to make 

 special provision for getting rid of carbonic 

 acid gas; and it is not probable that you will 

 ever have occasion to make any such arrange- 

 ments for its disposal. 



In what would be termed "pure country 

 air," carbonic acid is present in the propor- 

 tion of about 4 parts in 10,000. In a crowded 

 and confined space, such as the pit of a thea- 

 tre and in some school-rooms, its proportion 

 has been found to rise to 30, 40 and even 100 

 parts per 10,000. 



Pure carbonic acid gas may be present in 

 air in a proportion as high as 1.50 parts per 

 10,000 without producing discomfort or giv- 

 ing any special evidence of its presence, as for 

 instance in those establishments where spark- 

 ling mineral waters are bottled, or soda foun- 

 tains are charged, or in vaults where cham- 

 pagne is bottled, in certain rooms in breweries, 

 or in some celebrated baths and health re- 

 sorts. 



It is evident, therefore, that carbonic acid 

 gas — in the proportions in which we find it in 

 our worst ventilated rooms — is not in itself 

 a dangerous impurity; in fact, we have no ev- 

 idence to show that in such proportions it is 

 even injurious. 

 Dangerous Because Found in Bad Company. 



What, then, is the importance of this gas 

 in relation to questions of ventilation ? And 

 why do sanitarians lay so much stress upon 

 the results of chemical tests of air with refer- 

 ence to this body, and on what may seem 

 very small variations in the proportions in 

 which it is present ? 



It is because carbonic acid is usually found 

 in very bad company, and that variations in 

 its amount to the extent of three or four 

 parts in ten thousand indicate corresponding 

 variations in the amount of those gases, 

 vapors, and suspended particles which are 

 really offensive and dangerous, and because 

 we have tests by which we can with compar- 

 ative ease and certainty determine the varia- 

 tions in the carbonic acid, while we have no 

 such tests of recognized practical utility for 

 such other dangerous impurities. 



As a matter of convenience, therefore, we 

 measure the carbonic acid, and thus get a 

 measure of the extent to which ventilation is 

 being effected. Of course we must make 

 sure that the circumstances of the case pre- 

 sent nothing unusual, since, on the one hand, 

 carbonic acid may be present in great excess — 

 as in a soda fountain charging room — without 

 indicating great impurity; and, on the other, 

 it is possible that the air of a room may be 

 very dangerous, from suspended organic par- 

 ticles, and yet have carbonic acid present in 

 merely normal amount. 



Perhaps it seems to you that all this is.of 

 little interest to a "practical architect," but, 

 unless you know it very thorou.ghly indeed, I 

 fear that the formulas and specifications for 

 ventilation which you desire to learn will not 

 be of much use to you. 



AGRICULTURE IN THE SCHOOLS. 



In some of the Western Slates they are 

 moving to have the principles of agriculture 

 and horticulture taught in the public schools. 



If there are not too many things taught at 

 once in this way already, there would be good 

 results from such a course. But at present 

 every one who has had experieiicfc believes 

 that enough is taught now for the pupil's 

 good. In "ibis State, at least, the children 

 are taught such a variety of branches that 

 the regular school hours are not sufficient, and 

 the children have to spend most of the after- 

 noon, and best part of the evening afterward, 

 in learning the lessons for to-morrow. The 

 hardy and health-giving exercise of play has 

 hardly any time allowed it to perform the ne- 

 cessary part of making a vigorous body for 

 the mind's dwelling-place; and thus the great 

 school efforts result in much le.ss practical 

 good than the simple education of the past 



i'S'e- . ,_. ^, 



But we think there is one way in which 

 some good might result from some such an 

 education as that proposed. Instead of hav- 

 ing horticulture and agriculture taught regu- 

 larly in the schools, iiave a set day or half 

 a-day say every month for a visit to some 

 farm or garden, and there with practical re- 

 sults of the garden and held before them let 



