466 



KNOWLEDGE. 



December, 1913. 



eastern side of the Taff Valley to Cilfynydd, whence it roared 

 up Cwm Eldeg, and then over the north-eastern flank of 

 Llanfabon Mountain, and down into the Taff Valley. From 

 here it rushed up the western side of the valley, and expended 

 its fury upon the highest houses in Abercynon. It then seems 

 to have turned off at a tangent to Quaker's Yard and Treharris, 

 where its career apparently ended. The track of the tornado 

 was only about two hundred yards in width, but within this 

 area everything was devastated. Mr. Clement Edwards, M.P., 

 in an appeal for monetary help for the sufferers, states that 

 many hundreds of houses have been ruinously damaged, and 

 that over two hundred families have lost beyond repair most 

 of their furniture and all their bedding and bedclothes and 

 wearing apparel. Among the more extraordinary effects of 

 the storm it may be mentioned that half a corrugated iron 

 roof was carried for several miles, through valleys, across 

 villages, and over mountain tops, and the tins of the sheets 

 detached and wound round posts as a doctor wraps a bandage 

 round a broken wrist. A four-ton oak tree was carried away 

 for nearly a quarter of a mile. Unfortunately two men lost 

 their lives, one being caught by the fury of the storm and 

 hurled a distance of one hundred and fifty yards into a field, 

 and the other being struck on the head by a slate. 



EFFECT OF ATMOSPHERIC CONDITIONS ON 

 WIRELESS SIGNALS.— Dr. E. VV. Marchant read a paper 

 at the recent meeting of the British Association on the effect 

 of atmospheric conditions on the strength of wireless signals 

 sent out from the Eiffel Tower in Paris at 10.45 a.m. and 

 11.45 p.m., and received at Liverpool. The results obtained 

 show that there is a maximum variation from 0-6 to 1-3 in 

 the strength of the signals received on different days in the 

 same month ; the average strength of signal being assumed to 

 be 1-1, and that the current received on a fine clear night is 

 about 1 • 7 times as strong as that received in the daytime. 



Although no certain relationship can yet be regarded as 

 established between the strength of a signal and the weather 

 conditions at the sending and receiving stations, so far 

 observation has shown that rain in Paris always corresponds 

 with diminution in strength of received signal. In one case, 

 with a wind of six meters per second velocity, blowing in a 

 north-west direction, the signal-strength fell to half its normal 

 value. The most favourable condition for signalling appears 

 to be a cloudy sky at both sending and receiving stations, the 

 signals being weaker when the sky is clear or covered with 

 light clouds. Rain at the receiving station appears to have a 

 comparatively small influence on the strength of the received 

 signals. The result of a set of special signals sent from the 

 Eiffel Tower on the evening of Saturday, July 26th, 1913 (by 

 the courteous arrangement of Comm. Ferri6), at intervals of 

 thirty minutes, between 7 and 10 p.m. (which includes the 

 time of sunset), shows that the increase in strength of night 

 signals occurs just after sunset, there being an abrupt increase 

 in strength of about 70 per cent. This change is quite 

 sudden, there being comparatively little alteration in signal- 

 strength until the sun has set, and no perceptible increase in 

 strength afterwards. There appears to be some evidence that 

 signals are slightly stronger just after sunset than during 

 normal night conditions. 



MICROSCOPY. 



By F.R.M.S. 

 DENDROMONAS VIRGARIA WEISSE.— At one of the 

 excursions of the Quekett Club during the autumn the above- 

 named organism was obtained in some quantity ; though 

 probably not very rare, it is certainly not frequently recorded. 

 Owing to its exceeding transparency and delicacy, and the 

 small size of the composing units, it would be easily over- 

 looked by anyone unacquainted with it. Saville Kent gives an 

 excellent representation of it from which Figure 535 is taken.* 

 As will be seen it is a tree-like form. The stem, called the 

 " zoodendrium," is rigid, dichotomous, and copiously branched. 

 At the end of each branch is attached a somewhat flattened 

 pear-shaped animalcule, the forward end obliquely truncated. 

 It has two flagella of unequal length, and is without a mouth, 



food being taken in at all parts of the body. It has a nucleus 

 and one or two contractile vacuoles, and is practically a 

 stalked monad. The whole is perfectly transparent, and while 

 the individuals are extremely small — about 8m in length — the 

 entire organism is of considerable size, often consisting of 

 more than one hundred zooids, and being about 1-130" in 

 height. In consequence it is very difficult to observe satis- 

 factorily. For finding it and for a general view a half-inch 

 objective with good dark background illumination answers, 

 but for anything like a complete examination the highest 

 power that can be brought to bear on the object is necessary, 

 with a careful adjustment of light ; the use of a coloured screen 

 is advantageous. In the present instance, specimens were 

 fairly numerous on some fine grass stems which had evidently 

 been submerged a long time, but it was not found possible to 

 preserve them long under examination, as the zooids 

 soon became detached from the pedicle ; the stem 

 and branches, however, remained visible afterwards. In 

 most of the specimens it was noticeable that the 

 animalcules were arranged on a more regular level than 

 the illustration indicates, the mass forming, when looked at 

 from the side, a thin plate on the top of the beautifully 

 hyaline regularly-branched stem. In a surface view, at 

 least in the larger specimens, the pear-shaped bodies were seen 

 considerably compressed towards the middle of the group 

 owing to crowding, and were often angular in consequence. 

 Kent says of it : " Among all of the numerous stock-building 

 pedicellate varieties of the Flagellata, few, perhaps, excel the 

 present one in the exuberance of growth and graceful 

 symmetry of the erect branching zoodendrium. The 

 associated colonial stocks have been observed in such 

 abundance on the finely-divided leaves of Myriophyllum and 

 other water plants as to present the aspect of a perfect 

 forest growth of tiny crystal trees, each terminal leaflet replete 

 with life, and quivering with the combined vibratory action 

 of their flagella." Figure 535 represents an adult colony ; at 

 A is an isolated monad under high magnification ; and at B 

 a colony of two monads in process of longitudinal division, 

 all from Saville Kent's " Manual of the Infusoria." 



JAS. BURTON. 



QUEKETT MICROSCOPICAL CLUB.— October 28th, 

 S. C. Akehurst, " A changer for use with substage condensers." 

 This was on the principle of the Zeiss sliding objective 

 changers. 



S. C. Akehurst, " A trap for free-swimming organisms." 

 This was exhibited in two forms and took advantage of the 

 phototropism exhibited by most pond animals. 



James Murray, '" The Gastrotricha " : a valuable contribu- 

 tion dealing with this small group of minute animals, chiefly 

 freshwater, and of doubtful affinity. The paper describes 

 their form and structure, their haunts and habits, gives a 

 historical sketch of the group with its classification, a key to 

 the genera, and a list of the eighty-three species, including 

 one new one, which have been described, and concludes with 

 a lengthy annotated bibliography. The paper, with a plate of 

 some forty figures, appears at length in the November issue of 

 the Club's Journal. 



E. M. Nelson on "An improved form of Cheshire's 

 Apertometer" and M. A. Ainslie, " A variation of Cheshire's 

 Apertometer " ; two papers describing improvements designed 

 to facilitate and render accurate determinations of the second 

 decimal place of N.A. with this instrument. 



F.J. Cheshire did not think the form of Apertometer he had 

 introduced some ten years ago capable of greater accuracy 

 than he had then given it. He described another method of 

 estimating N.A. which he considered an improvement on the 

 older one. 



PHOTOGRAPHY. 



By Edgar Senior. 



TESTING FOR "HYPO" IN MOUNTS, PRINTS, 

 AND WASHING WATER.— If silver prints are mounted 

 upon card that contains traces of " hypo " owing to this body 



" Manual of the Infusoria." Plate XVII, Figure 1. 



