December 80, 1869. ] 



JOUENAL OP HOBXIOULTDRE AND COTTAGE GARDENER. 



517 



hnndred-petaled ones, vying with the Rose for beauty, the 

 fragrance, alas ! wanting. I have often wondered that these 

 gems were not more cultivated, and a succession of sowings 

 would carry on the bloom till late in the autumn. Sunshine 

 they muBt have, and they blossom best on a rather poor soil. 

 — Devon. 



[We omitted the last sentence'in your note. From expe- 

 rience we can testify the persecution it occasions to the ge- 

 nerous. — Eds.] 



MOISTURE IN THE AIR OF A VINERY. 

 HYGROMETERS. 



1st, What amount of atmospheric moisture is proper to be 

 kept in a vinery in the different stages of growth ? Also what 

 is the best way of constructing a hygrometer, or for what price 

 and where can a moderately good one be purchased? The 

 Vines are started on the Ist of February. 



2ndly, Last year my Vines were started on the 23rd of 

 January. In March and April, when in leaf, we had several 

 fierce sunny days, but with a sharp, cutting, easterly wind, and 

 in giving air to keep down the temperature the leaves suffered 

 severely, the greater part of them turning quite yellow. I shall 

 be glad to know what is the best management for a vinery under 

 such circumstances as the above, both as to giving air and 

 moisture, so that the leaves may be kept healthy. — T. H. D. 



[The subject is a very large one and to go into it fully 

 would require more details than could be entered upon in a 

 short answer, or even an article. We cannot give you the 

 prices of hygrometers, as they vary according to the kind, the 

 workmanship, and the nicety of observation required, and in- 

 structions generally accompany the instruments. Of these, 

 Daniell's we still consider the best. There are many simple 

 hygrometers which sufficiently tell roughly the vapour exist- 

 ing in the atmosphere, such as pieces of wood, and long hairs 

 deprived of their oily matter by washing in hot water contain- 

 ing a little dissolved soda; any textile fabric, as flax, will 

 always tell in a rough way, and so will any kind of cord, cat- 

 gut, seaweed, (tc. We know many farmers who keep a piece 

 of seaweed in their sitting-room, and depend as much on that 

 as the best of barometers. When there is much vapour it 

 becomes soft and clammy to the touch ; when the air is dry 

 the seaweed is also dry. All the cords and textile fabrics 

 alluded to above contract in a damp atmosphere and lengthen 

 in a dry one. We once had a very use'n^ simple hygrometer. 

 It consisted of a piece of catgut 6 feet long ; one end of this was 

 fixed by a pin to the wall, and the catgut was taken horizontally 

 about half its length, and then turned over a wooden peg with 

 a groove in it, the loose end hanging down perpendicularly, with 

 a small piece of lead attached to it to keep it so, and in that lead 

 a peg or pin of 2 inches long, or so, was fixed, so as to pass up 

 and down in front of a slip of wood some 18 inches long, 

 with lines made across with a pen at regular distances. The 

 pin or index rose or fell, just as the catgut contracted or 

 lengthened. 



Next to Daniell's hygrometer for correctness, and, perhaps, 

 the simplest as formed on the same principle, is merely to 

 have two thermometers suspended close to each other, and 

 which are seen to denote, when left alone, the same degree of 

 temperature. Place one wrap of white muslin or silk round 

 the bulb of each thermometer. Leave then the bulb of one 

 thermometer dry to denote the temperature of the atmosphere. 

 Keep the bulb of the other thermometer, with its covering, wet, 

 by a phial or other vessel of pure water suspended over it, and 

 a thread of floss silk or fine wool passing from the vessel to 

 the bulb. The difference in temperature between the dry and 

 the wet bulb enables us to measure the amount of vapour 

 in the air of the house. Thus, supposing both bulbs were 

 within from 1 to C of the same temoerature, we should con- 

 sider that the humidity was quite ample. Should even the wet 

 bulb fall to as much as 7° to 10' below the dry one, there would 

 not be much cause tor alarm in general ; but when the dif- 

 ference reached 12' or 15', or more, then the extra dryness 

 would become dangerous, and especially in cjld frosty nights. 



Now, to apply the above, so as to give an answer to your 

 second inquiry, in all glass houses the greater the difference 

 between the external and the internal air, the greater the 

 necessity of attending to atmospheric moisture. Hence, on 

 this account alone, a comparatively low safe temperature at 

 night is not only safest and healthiest for most of the plants 

 we grow in forcing heat, but it involves least trouble as respects 



the necessary atmospheric moisture. Much less attention will 

 also be required in houses whose glass roofs are close, without 

 laps, and also somewhat in proportion to the thickness oi the 

 glass, as, other things being equal, the thicker the glass the 

 more heat will it keep in, and therefore in a cold night there 

 will be less condensation of moisture on its inner surface, that 

 condensation always tending to make the air drier. The 

 greater, therefore, the difference between the internal and the 

 external temperature, the greater will be the condensation, and 

 that much more than in an arithmetical ratio. This condensa- 

 tion is one of the causes of the air in bouses becoming too dry. 

 It has been computed that each square foot of glass of ordinary 

 thickness will cool 1; foot of internal air as many degrees per 

 minute as the temperature of the inner air exceeds that of the 

 outer air. Thus, if the outside air should be 30°, and the 

 inside C0°, the vapour in the 30° difference would be precipi- 

 tated or condensed against the glass or bare, and either run out 

 of the house or hang or drop in it. The capacity of air for 

 moisture is greater the higher the temperature, and that much 

 more than in a regular gradation. Thus, air at ti6° will hold 

 a double amount of invisible vapour as compared to what it 

 would do at 44° ; but it will hold three times as much at 80^ 

 and four times as much at 'JO", and so on. Air escaping at 80° 

 takes out with it four times as much vapour as would come 

 in with air at 44°. An idea may therefore be formed of the 

 parching effects of letting air out of a house, say at G.">', and 

 admitting frosty air at 20°. A second chief cause, therefore, 

 why the air of a high-temperatured house becomes overdry, is 

 the free escape of the heated moist air against our will threngb 

 laps in the glass and other crannies, and our voluntary ad- 

 mission of the cold air by ventilation. A third mode of over- 

 drying the air may be here referred to, and that is when such 

 porous materials as soft flues were used in houses with a high 

 temperature. Close hot-water iron pipes give jast as dry a 

 heat as the flue would do, but then the pipe from its hardness 

 cannot greedily, Uke a soft flue, suck in the moist vapour. 



Now for a practical application. We believe that much in- 

 jury in old times was the result of having an atmosphere too 

 hot and too dry ; and in modern times, though an atmosphere 

 saturated with vapour would tell most favourably on all annual 

 and succulent growth, and is most needed there, this extra 

 humidity, if maintained, would tell injuriously on the flavour 

 of fruit and the ripening of the wood. For deciduous plants, 

 such as the Vine, it is most needed when the shoots are young 

 and soft, and when the fruit is also small ; but as the latter be- 

 comes well swelled, the air of the bouse should become gradually 

 drier. We may take a lesson from what disappoints us as weU 

 as from that which succeeds. Many a Peach tree on the open 

 wall fails, if not in fruit, at least for a time in healthy shoots, 

 because when these shoots are young and soft the air is too 

 dry and parching for them. We can neutralise the dryness in 

 the houses, and here the simplest modes are generally the 

 most effectual. In the general run of plant houses, where the 

 forcing heat seldom goes beyond 45° or 50°, little or no trouble 

 need be taken about atmospheric vapour if ventilation be given 

 in moderation, and the external temperature should not be very 

 low; but in severe frost, when more firing is needed, it may 

 be necessary to damp the stages and the pathways, and even 

 the floor, with a syringe. Giving air sparingly, at the top of the 

 house will be much better than larger fires and accompany- 

 ing evaporating pans. The vapour rising from the pots and 

 the floor will, except under these circumstances of extra cold, 

 be quite sufficient. 



Then, again, in the case of Vines, little additional vapour 

 would be needed for the first three weeks of forcing, but as the 

 buds break and lengthen more will be required — that is, as the 

 heat of the house rises to 60° and onwards. Generally, evapo- 

 rating pans on the top of flues and pipes will be the best for 

 this purpose ; but on extra occasions, such as a bright sun in 

 sharp frost, the floors and pathways should be sprinkled in 

 addition, but in such cases less depends on additional atmo- 

 spheric moisture than in preventing it unduly escaping by 

 free ventilation, and this should be regulated by preventing 

 fire heat and sun heat acting on the enclosed atmosphere of a 

 house at one and the same time. The beams of the sun will 

 tell quite as well if there be no great openings in such cases 

 for the entrance of cold, dry air. In dull, mild weather out of 

 doors, less artificial vapour will be wanted than when the ex- 

 ternal air is cold and frosty. 



It is just possible that in a vineiy started on January 23rd 

 the leaves suffering severely in April, so as to turn yellow 

 during a few days' fierce stm and cutting east winds, might be 



