Aug. 18, 



• KNOWLEDGE 



197 



the artist, and it should be the aim of the photographer to 

 produce good photography. 



Retouching on the negative should not be attempted 

 until the varnish is quite hard. Pencils of diflerent 

 degrees of hardness will be needed, HHH, HH, HB, and 

 B are all useful, and they should be of the best quality of 

 lead. 



Vignettes require careful attention in printing. A piece 

 of cardboard should have an aperture cut roughly to the 

 shape of the portrait required, but somewhat smaller. This 

 cardboard shape should be placed about a quarter of an 

 inch from the negative, outside the printing-frame. A 

 piece of tissue-paper pasted over the aperture will soften 

 the light and produce the vignette effect. 



It might be supposed that the expansion of paper by 

 moisture would be equal in all directions. Experience 

 shows that this is not the case. It will sometimes be found 

 after the prints are mounted that some are larger than 

 others. This, of course, in a portrait, is a serious defect, 

 as it makes the face too long or too broad, as the case may 

 be. The prints ha^-ing all been cut to the same size, 

 it is easily seen when they are mounted if the paper in use 

 produces the defect; and should such be the case, the 

 prints must be allowed to become dry before mounting, 

 and then, if the starch be applied quickly, the paper has not 

 time to fully expand before it is attached to the mount. 

 The defect referred to should be looked for, as unless the 

 prints are compared with each other, it may escape notice, 

 and the portrait would possibly be found to be defective in 

 some way, and the true cause not be suspected. 



sKfbirtos. 



GUIDE TO SOUTHAMPTOX.* 

 This is a useful and cheap little guide to Southampton, 

 written expressly for the %-isit of the British Association 

 for the Advancement of Science (the particulars of 

 which are given below). It contains an interesting 

 sketch of the ancient history of Southampton ; an 

 account of the streets and public buildincjs, parks, 

 quays, chapels, and so forth ; a sketch of the shipping 

 companies connected with the port ; and a sufficient 

 description of excursions, drives, and walks in the neigh- 

 bourhood. 



THE BRITISH ASSOCIATION. 



THE .arrangements for the fifty-second annual meeting of this 

 association, which is about to be held at Southampton, ex- 

 tending from Wednesday, the 23rd inst., to Thursday, the 31st, arc 

 now completed, and an elaborate official programme has been 

 issued. The first general meeting will bo held on Wednesday 

 evening at the Victoria Skating Rinlc, when Sir John Lubbock will 

 resign the chair to Dr. C. W. Siemens, and the president-elect will 

 give his inaugural address. On Thursday evening there will bo a 

 soiree in the Hartley Institution at the invitation of the Local 

 Executive Committee ; on Friday evening a " Discourse on the 

 Tides," by Sir William Thomsonj M.A., in the Skating Kink ; on 

 Monday evening a discourse on " Pelagic Life," by Mr. H. N. 

 Moseley, M.A., at the Skating Rink ; on Tuesday evening a soiree 

 at the Hartley Institution on the invitation of the Mayor and Cor- 

 poration; and on Wednesday afternoon the concluding general 

 meeting at the Skating Kink. The several sections will meet daily 

 at 11 o'clock in the morning from Thursday to Tuesday, both 

 inclusive, in various public buildings. The gcnornl committee 

 will meet on the 23rd for the election of the President and 

 sectional officers ; on the 28th, to appoint officers for 1883 



• " Guide to Southampton and Xeighbourhoo<l." By Thos. W. 

 Shore, F.G.S., F.C.S. Published by Gutch & Cox, Southampton. 

 Price Eightponco. 



and the place of meeting in 1884 ; and on the 30th, when 

 the report of the committee of recommendations will be 

 received. On Saturday afternoon, the 26th, there will be 

 five half-day excursions to various places of interest in the neigh- 

 bourhood, including one to Broadlands and Komsey, where Lord 

 Mount-Temple will entertain the visitors, and another to Xctley 

 Abbey and Hospital, where a garden-party is to be given by the 

 Surgeon-General and officers of the Army Medical Department. On 

 Thursday, the 31st, four whole-day excursions are arranged, some 

 on water, and some on land. The Bishop of Truro will preach a 

 sermon at St. Mary's Church on the morning of Sunday, the 27th, 

 when the members and associates, with the Mayor and Corporation, 

 will attend the service, and on the same morning the Kev. C. 

 Pritchard, Savilian Professor of -Astronomy at Oxford University, 

 mil preach at All Saints' Church. Canon Basil and Mrs. Wilber- 

 force give a garden-party in the deanery grounds on Monday, the 

 2Sth, and on the evening of the same day the Provincial Grand 

 Master of Hampshire and the Isle of Wight will offer a Masonic 

 welcome to visiting brethren. The Queen has assented to an appli- 

 cation for the members of the association to visit Osborne after her 

 departure for Scotland, which will probably be about the 25th inst. 

 Various other arrangements of a minor character have been made 

 to give a proper reception to the Association during its visit. Out- 

 side the immediate engagements of the Association, a lecture to the 

 operative classes is to be given in the Skating Rink on Saturday 

 evening by Mr. John Evans, D.C.L., on " Unwritten History, and 

 how to read it," the chair being taken by Dr. Siemens, the new 

 president. 



A LUMINOUS SHARK 

 By C. F. Ugldee. 



AMONG the later outgrowths of scientific investigation we find 

 the theory of abysmal light, intended to explain the presence 

 of eyes in many of the deep sea forms, their existence supposed to 

 be conditional upon the presence of light in the greater depths of 

 the ocean. The Ascidians and Alcyonarians are well known as 

 wondrous b'ght givers. The form of the former we are most 

 familiar with is the oval ball that seems growing upon a stem, and 

 waves to and fro with the tide like a veritable plant ; it is, how- 

 ever, a highly organised animal. Some of the Ascidians are free 

 swimmers, and live in colonies ; such is the Pyrosoma, one of the 

 most remarkable of all phosphorescent creatures, as well as one of 

 the largest. In appearance they resemble an elongated empty 

 barrel, about 5 ft. long as a maximum, with one end closed, the 

 other open, a proWsion that insures movement in a given direction. 

 The means of propulsion seems incomprehensible, but it is easily 

 explained, however, upon an examination of the animal. Each 

 individual in the colony draws in water from the outside and ejects 

 it into the interior, where it finds a common outlet at the open end, 

 the ciurent rushing out forcing the aggregation of Ascidians along 

 in the direction it happens to take. The surface is completely 

 covered with curious filaments that appear to wave to and fro. 

 Such is the general appearance of the creature in the daytime, but 

 in the night or abysmal depths of the ocean it presents an entirely 

 different sight, gleaming and glowing with a wondrous golden light, 

 that penetrates the water for twenty or thirty feet around it, and 

 resembling more than anything else a cylinder at white heat, vi- 

 brating waves seeming to pass over it in quick succession, pro- 

 ducing many different tints of yellow and gold. As may bo surmised, 

 at a distance of one hundred feet or more they resemble 

 worms three or four feet in diameter, of wavy, nebulous 

 matter, the centre burning brightly. The appearance of num- 

 bers of these wondrous creatures in the water is an ex- 

 traordinary sight, and looking down into the depths we seem 

 to be looking into space. Every break of the water is the 

 signal for myriads of beautiful creatures to spring into life, as it 

 were, the sea fairly igniting tho minute granules in the depths 

 l)elow sparkling and scintillating in the reflection. Great constella- 

 tions seem revolving in erratic courses, now rising and falling, 

 meeting each other, the lights intermingling, while smaller phospho- 

 rescent jelly fishes, like stars of lesser magnitude, revolve about 

 them, completing the curious scene. The light given out by the 

 Pyrosoma is not confine<l to tho water, but is letlectcd above it, 

 covering everything with a pale, ghostly light. The snils of vessels 

 are lighted up by it, and cast dark shadows al)out, while within four 

 or five feet vf tho animal a newBpa|>cr can be read with perfect 

 ease. 



But the most curious light-giving forms discovered are the fishes. 

 Among the bony fishes of grvat depths, the families Scopolids, 

 Stcnioptychids, and Stomiatids have long nttmcted attention, on 

 account of the rows of bright spots that ocotir upon their sides, 

 now found to bo luminous. These arc found pspocially upon the 

 fishes ChauUodv$ Sloani, St'>miai boa, Scoptlut liumMdii, Ac. In 



