is on the driest and most exposed part of the mounds that the plant occurs. Its change from such a poor position to our garden, which though only unmanured forest marble-clay, is yet moist and stiff, will doubtless account for its wonderful growth.

Cuscuta epilinum.-Our last year's report on experiments in the growth of this Dodder excited so much attention, that we determined upon following out some additional ones in the present season, to which end we sowed two plots with flax-seed, as follows:

Plot 1. Flax seed perfectly pure.-The result was a very fine crop, perfectly clean.

Plot 2. Dirty Flax-seed with some seeds of Cuscuta epilinum intermixed.— This was scarcely half a crop, and the fine specimens of Dodder bearing down the partial crop, is at once an evidence of the mischief this parasite can do to the crop in question, as also of the perfect ease with which we can grow it; so also how easy to prevent its presence in the flax-crop if we take care to sow pure seed.

As regards the Clover Dodder, though this pest is yearly becoming more and more prevalent, yet this season has been especially bad for ripening its seed, and we are still in want of seed for special experiments upon it.

Seeds of Orobanche minor have been collected this year with a view to a series of experiments upon it, as the Broomrape, like the Dodder, is yearly becoming more and more troublesome; and it would seem that Clovers are liable to attacks from both forms of the parasite, and in all probability of more than a single species of either; for, as regards Broomrape, we have collected the two forms O. minor and O. elatior from different Clover crops; we still want to know whether the Cuscuta europæa and C. Trifolii are specifically distinct.

Myosotis. We last year reported upon some curious changes wrought in the cultivation of M. sylvatica, in which we gave it as an opinion that the M. palustris of authors was subject to great variations, giving rise to annual as well as perennial forms, the former introducing us to the M. sylvatica and others, as offsprings of M. palustris. Our present stock still bears out this view, as we have as derivatives from M. sylvatica a still decreasing flowered form and annual and perennial conditions of our varieties.

This year we introduced into the garden the very bright blue Forget-menot of our ditches; this in cultivation (the same plant) has become the small flowered light blue form which we take to be the M. repens of Don, as described by Mr. Babington.

While upon this subject we must not omit to mention that, having been favoured with a packet of seed from the eminent firm of J. Carter and Co. of Holborn, under the name of Myosotis azurea major, we were much interested in observing what kind of bedding plant it might make, particularly as in the Seed Catalogue for February 1860 we find the following remarks appended to the Myosotis species :

Forget-me-not. These beautiful flowers are too well known to need recommendation: will grow around fountains, over damp rockeries, or in any moist situation. M. azorica and azurea major are the finest."

Of course, from this announcement we expected something rather choice; but our disappointment may be guessed when we found the result to be a very poor small light-coloured variety of M. palustris.

Now, we are far from blaming the Messrs. Carter for this, as it will at once be seen that this was an induced form, and no one can at all answer for its permanency; and it may be that our position or some new circumstances of cultivation induced the change from an expected fine flower to a very insig

nificant one. Still this affords another curious instance of the effects of cultivation upon this genus, which seem to tell us that we must not be too positive in the specific distinctions adopted by authors for these plants.

The effects of the season of 1860 have been remarkable in several particulars; we would, however, only refer to a few plants under experiment. Dioscorea Batatas, Potato Yam.-Smaller than ever; cannot be at all depended upon, even to make its seed in the Cotteswold district.

The Cabbage tribe sadly cut up with us, but the Brussels Sprout was found to be the most hardy of any kind.

Gyneria argentea.-Killed entirely, both in the College and our own private garden.

Sorghum saccharatum.-Scarcely attained 6 inches in height against 7 feet of the previous year.

Zea Mays.-Indian corn not 2 feet high, and died as soon as flowered. Roots of all kinds smaller than usual.

Potatoes small in quantity and much diseased.

Fruits have not attained their usual size, have not ripened, and are flavourless.

Forest trees have made little wood, and their new shoots are not ripened. Garden flowers made little growth, shabby both in leaves and flowers. Plants perfected for less seed than usual.

Cirencester, November, 1860.

Report of the Committee requested "to report to the Meeting at Oxford as to the Scientific Objects to be sought for by continuing the Balloon Ascents formerly undertaken to great Altitudes." By the Rev. ROBERT WALKER, M.A., F.R.S., Reader in Experimental Philosophy in the University of Oxford.

In presenting their Report, the Committee would observe at the outset that the main object for which the former Committee (in 1858) was appointed remains yet unaccomplished; and this is the verification of that remarkable result derived from the observations of Mr. Welsh in his four ascents in 1852, viz."the sudden arrest of the decrease in the temperature of the atmosphere at an elevation varying on different days, and this to such an extent, that for the space of 2000 or 3000 feet the temperature remains nearly constant or even increases to a small amount." It is obviously important to determine whether this arrest represents the normal condition of the atmosphere at all seasons of the year. The ascents of Mr. Welsh were made between the 17th of August and the 10th of November. The question remains, whether this "arrest" would be observed before the summer solstice as well as after, and whether there were any variations at different seasons. The changes in the temperature of the dew-point, consequent upon this interruption in the law of decrease of temperature, would extend our knowledge of the condition of the atmosphere at such altitudes. To accomplish thus much would not require ascents to very great altitudes, although there are many objects to be attained by ascending as high as possible. The liberal offers that have been made by Mr. Coxwell and Mr. Langley, of Newcastle, would enable observations to be made at a very moderate cost, and Mr. Langley appears fully competent to accomplish the task. There are also many other observations which may be made in balloon ascents which

may prove of very great value. Prof. W. Thomson is anxious that observations should be made on the electrical condition of the atmosphere. He has described in the article on the Electricity of the Atmosphere in Nichol's 'Cyclopædia,' a portable electrometer, and also a mode of collecting electricity by that which he styles the water-dropping system, which would, in his opinion, be easily applicable. The observations might be carried on, first, by ascending to very moderate heights, and then going as high as possible. Dr. Lloyd desires that observations should be made for "the determination of the decrease of the earth's magnetic force with the distance from the surface." The failure of Gay-Lussac to detect any sensible change ought not to deter future observers. His methods were wholly inadequate; but Dr. Lloyd is of opinion that if attention be confined to the determination of the total force or its vertical component (instead of the horizontal), it would be easy to arrive at satisfactory conclusions. Sir David Brewster suggests that further information may be obtained as to the polarization of the atmosphere and the height of the neutral point. And, lastly, Dr. Edward Smith and Prof. Sharpey are desirous that experiments should be made as to "the quantitative determination of the products of respiration at different high elevations." Dr. Smith has, as it is well known, been for the last two or three years engaged in experimental inquiries on inspiration, and he is so satisfied of the value and importance of the investigation, that he is not only willing, but desirous to make the requisite experiments himself. Dr. Smith has furnished directions as to the points to be observed and the mode of observation.

Report of Committee appointed to prepare a Self-Recording Atmospheric Electrometer for Kew, and Portable Apparatus for observing Atmospheric Electricity. By Professor W. THOMSON, F.R.S. YOUR Committee, acting according to your instructions, applied to the Royal Society for £100 out of the Government grant for scientific investigation, to be applied to the above-mentioned objects. This application was acceded to, and the construction of the apparatus was proceeded with. The progress was necessarily slow, in consequence of the numerous experiments required to find convenient plans for the different instruments and arrangements to be made. An improved portable electrometer was first completed, and is now in a form which it is confidently hoped will be found convenient for general use by travellers, and for electrical observation from balloons. A house electrometer, on a similar plan, but of greater sensibility and accuracy, was also constructed. Three instruments of this kind have been made, one of which (imperfect, but sufficiently convenient and exact for ordinary work) is now in constant use for atmospheric observation in the laboratory of the Natural Philosophy Class in the University of Glasgow. The two others are considerably improved, and promise great ease, accuracy, and sensibility for atmospheric observation, and for a large variety of electrometric researches. Many trials of the water-dropping collector, described at the last Meeting of the Association, were also made, and convenient practical forms of the different parts of the apparatus have been planned and executed. A reflecting electrometer was last completed, in a working form, and, along with a water-dropping collector and one of the improved common house electrometers, was deposited at Kew on the 19th of May. A piece of clock

work, supplied by the Kew Committee, completes the apparatus required for establishing the self-recording system, with the exception of the merely photographic part. It is hoped that this will be completed, under the direction of Mr. Stewart, and the observations of atmospheric electricity commenced, in little more than a month from the present time. In the mean time preparations for observing the solar eclipse, and the construction of magnetic instruments for the Dutch Government, necessarily occupy the staff of the Observatory, to the exclusion of other undertakings. It is intended that the remaining one of the ordinary house electrometers, with a waterdropping collector, and the portable electrometer referred to above, will be used during the summer months for observation of atmospheric electricity in the Island of Arran. Your Committee were desirous of supplying portable apparatus to Prof. Everett, of Windsor, Nova Scotia, and to Mr. Sandiman, of the Colonial Observatory of Demerara, for the observation of atmospheric electricity in those localities; but it is not known whether the money which has been granted will suffice, after the expenses yet to be incurred in establishing the apparatus at Kew shall have been defrayed. In conclusion, it is recommended to you for your consideration by your Committee, whether you will not immediately take steps to secure careful and extensive observations in this most important and hitherto imperfectly investigated branch of meteorological science. For this purpose it is suggested,-1. that, if possible, funds should be provided to supply competent observers in different parts of the world with the apparatus necessary for making precise and comparable observations in absolute measure; and 2. that before the conclusion of the present summer a commencement of electrical observation from balloons should be made.

Experiments to determine the Effect of Vibratory Action and longcontinued Changes of Load upon Wrought-iron Girders. By WILLIAM FAIRBAIRN, Esq., LL.D., F.R.S.

AMONGST engineers opinions are still much divided upon the question, whether the continuous changes of load which many wrought-iron constructions undergo, has any permanent effect upon their ultimate powers of resistance; that is, whether a beam or other construction subjected to a perpetual change of load, would suffer such an alteration in the structure of the iron or the tenacity of the joints, that it would in time break with a much less force than its original breaking weight. But few facts are known, and few experiments have been made bearing on the solution of this question. We know that in some cases wrought iron subjected to continuous vibration assumes a crystalline structure, and is then deteriorated in its cohesive powers; but we are yet very ignorant of the causes of this change, and of the precise conditions under which it occurs.

A few experiments were made by the Commission appointed to inquire into the application of iron to railway structures, to ascertain the effect of changes of load upon homogeneous bars of wrought and cast iron. They found with cast iron that no bar would stand 4000 impacts, bending them through one-half of their ultimate deflection, but that sound bars would

sustain at least 4000 impacis, bending them through one-third of their ultimate statical deflection. They ascertained also, that when the load was placed upon the bars without impact, if the deflection did not exceed onethird of the ultimate deflection, the bar was not weakened; but that if the deflection amounted to one-half the ultimate deflection, the bars were broken with not more than 900 changes of load. With wrought iron bars they found no perceptible effect from 10,000 changes of load, when the deflections were produced by a weight equal to half the statical breaking weight.

These experiments are interesting so far as they go, but they are very incomplete as regards wrought iron. For wrought-iron bars they were not continued long enough, nor do they apply to those larger constructions in which the homogeneous bar is replaced by riveted plates. The influence of change of load on riveted constructions possesses a special importance, from its bearing on the question of the proper proportion of strength in plate and tubular bridges. Do these constructions gradually become weakened from the continual passage of trains? and is it requisite to make allowance for such a deterioration by increased sectional area of material in their original construction? These questions I have sought to solve by the following experiments.

As the load is brought upon bridges in a gradual manner, the apparatus is designed to imitate as far as possible this condition. A riveted beam is fixed on brickwork supports, 20 feet apart. Beneath this is placed a lever grasping the lower web of the beam, and fastened upon a pivot at the fulcrum. At the other extremity it carries the scale and weights. This lever is lifted clear of the beam, and again lowered upon it by means of a connecting rod attached to one of the arms of a spur-wheel placed at a considerable distance overhead. In this way any required part of the breaking weight can be lifted off and replaced upon the beam alternately by the revolution of the spur-wheel. The apparatus is worked night and day by a water-wheel, and the number of changes of load is registered by a counter.

The girder subjected to vibration in these experiments is a plate girder of 20 feet clear span, and of the following dimensions :

This beam having been loaded with 6643 lbs., equivalent to one-fourth of

the ultimate breaking weight, the experiment commenced.