August 2, 1886.] 



♦ KNOWLEDGE ♦ 



o 1 n 



olo 



In part these .are brought about by arbitrary but oft 

 repeated motions, inasmuch as such will gradually take 

 place more rapidly and without premeditation. 



In this way, through practice, counting from one to five 

 is done unconsciously, and somewhat resembles a reflex 

 action. 



If many such simple mental acts (by the repetition of 

 which nothing new is learned, and time only is lost) could 

 be caused to pass off more rapidly — somewhat resembling 

 reflex- actions — the brain would be left free to turn to other, 

 to higher aims. — Translated for tlie " Popular Science 

 Montldij " J'ro)ii " Die Gartenlaube." 



THE NATURALIST'S LABORATORY. 



COXTRIBUTIOS 11. 



^ HERE are many items of importance to be 

 attended to in the choice and arrangement 

 of a special apartment for laboratory work 

 that are apt to be overlooked by the 

 majority of ordinary students, so that a 

 few words here upon the subject will not 

 be out of place. 

 First of all. with regard to light, pure diflFused daylight is 

 unquestionably the best, and the window or windows ought 

 therefore to face the north, and command, if practicable, a 

 wide expanse of sky. The room need not be a large one, 

 but, whatever its size, every part ought to admit of being 

 jierfcctly lighted during the hours of sunlight, so as to allow 

 the most perfect inspection at any time. But, since a clear 

 north light cannot always he commanded, some eSicient 

 provi.sion should be made to modify the direct rays of the 

 sun which will then enter through the ordinary panes of 

 window glass, tlie transparent, colourless material of which 

 may be replaced by translucent ground glass, opal plates, or 

 covered over with a film of white paint or whitewash solu- 

 tion. A ready expedient can be adopted by interposing a 

 screen of white tissue paper or muslin ; but the.se last ought 

 to be removed and frequently cleansed, since they are very 

 apt to harbour dust, and may unexpectedly interfere with 

 the operator's work by an unlooked-for shower at any time. 

 For similar reasons carpets, rugs, and curtains must not be 

 admitted. By following this advice strictly, pure difl"used 

 daylight, only slightly inferior to an uninten-uptetl northern 

 light, will be obtained, and nought can interfere to damage 

 the student's most delicate work. 



The window was originally con-^tructed to act as a venti- 

 litorin ancient times — it was a ivi7id-door ; but nowadays 

 the advances that have been made in architecture show that 

 its true function is to li^/ht the apartment during the day. 

 time, and to act as a ventilator only in .a subordinate way. 

 Although professional architects are cognisant of these facts, 

 the greater number of houses in this country are not built 

 under their supervision, and are hence very imperfectly 

 constructed ; so much so that the windows are left to per- 

 form a principal duty in letting fresh air into the house. It 

 is thus highly probable that many persons may find their 

 chosen sanctum, with its north light, subject to violent 

 draughts, with their accompaniments of dust and dirt, 

 aggravated by occasional puffs of smoke from the fireplace 

 during the colder periods of the year. To correct all this 

 would te a great boon to the worker, for it would place it 

 in his power to at once free himself from his worst enemy, — 

 suspended dust, — and to derive much personal comfort 

 during his labours. We shall show in the sequel that the 

 remedy is not only extremely simple, Vnit inexpensive. 



The atmosphere of inhabited rooms differs from the normal 



fresh air both chemically and physically. The products of 

 combustion and respiration attendant upon lite and its 

 surroundings — fireplaces, lamps, gas, itc. — tend to vitiate 

 the air and render it eventually quite poisonous. But 

 although the density of the principal pernicious product, 

 carbon dioxide (C'0.j=22 when H^l), is greater than that 

 of the principal gases of air — viz. oxygen and nitrogen 

 (0=16, N = 14),yet the contaminated air rises to the upper 

 region of the room in virtue of the higher temperature with 

 which it is endowed by its generators, the fire, gas-flame, 

 and the lungs. As soon as it reaches the ceiling pro- 

 vision should be made for its expulsion, otherwise it 

 will have time to cool, descend, permanently pollute the 

 air, and give rise to latitude, sick headaches, and a 

 general disinclination for work. No doubt this could 

 be remedied by opening the window slightly both at 

 the top and bottom, but such a procedure would not be 

 likely to suggest itself during a cold wintry day, and in 

 warmer weather would admit extraneous dust and dirt. 

 Hence, if no special provision is made for the escape of the 

 foul air, it will descend and make its exit partially through 

 the chimney vent, but not until the conditions of pressure 

 within and out of doors have been so considerably altered 

 that a forced draught is caused through window chinks and 

 beneath the doors of the apartment. 



Efficient ventilation thus should provide for the extrac- 

 tion of the vitiated air at a point of vantage, and for the 

 equalisation of jjressure (to prevent draughts) by an inlet 

 for fresh air. Appliances without number have been in- 

 vented from time to time to meet these wants, but in every 

 case attention must be paid to the size and position of the 

 apartment to be ventilated. As a rule, however, it will be 

 found that for a moderate-sized lOom one outlet for vitiated 

 air will be sufficient, and that should be placed in or near 

 to the ceiling. The form known as " Boyle's Mica-Flap 

 Outlet Ventilator" should be fixed in the breast of the 

 chimney immediately beneath the cornice. The ventilator 

 consists of a metallic box with an open grating in front. 

 Behind the grating are suspended usually four valves of 

 mica, which are practically indestructible, light, ijnd rigid ; 

 they are so sensitive that they open with the slightest appre- 

 ciable up-current in the flue, and immediately close against 

 down-draughts, so as to effectually prevent the smoke from 

 entering the room. As a rule, the up-draught of the chim- 

 ney is sufficient to extract the foul air through the raica- 

 flap ventilator, but, to make things doubly secure, a chimney 

 cowl should be placed at the top of the flue. The action of 

 the latter is to draw up the air in the chimney, and those 

 constructed upon the passive principle are, without doubt, 

 the best. The slightest gust of wind over the chimney-top 

 induces a vacuum in the head of the cowl, and the foul air 

 is thus eflfectuall}' sucked up, as it were, and expelled at a 

 part where it cannot do any harm. 



A more perfect plan than that just detailed above would 

 involve a well-regulated system of ventilating pipes through- 

 out the house : a special pipe leading from the ceiling of 

 each apartment to an extracting ventilator on the roof, 

 independent of the fireplaces and chimneys. Such a .system 

 need not be expensive; indeed, it comes within the easy 

 reach of the poorest class of persons, for there are now 

 firms who make it their business to supply all the requisites 

 for efficient ventilation of houses or of i.solated rooms at a 

 very small cost. A case in point is noted in The Architect 

 for August 16, 1884 (pp. 100, 101), where the writer says 

 respecting the thorough ventilation of a workman's cottage 

 of about four rooms:--" It may be frankly stated that 

 Messrs. Boyle do not submit this system with any expecta- 

 tion of deriving a profit from the manufacture. It is intro- 

 duced simply for the benefit of the working and poorer 



