Atigtist 4, 1887] 



NATURE 



19 



335° + 49°, and 351° + 38°. All these are swift and short, and 

 generally devoid either of streaks or trains. 



Bristol, July 31. W. F. Denning. 



P. S. — In 1885 and some other years I have seen, on about 

 July 13, a very definite shower of bright streak-leaving meteors 

 from the point 11^ + 48°, and it is a very probable cjnjecture 

 that this radiant represents the earliest manifestation of the stream 

 of Perseids.— W. F, D. 



Floating Eggs. 



Referring to the remarks of Mr. E. E. Prince in Nature, 

 Tuly 28, p. 294, on the above subject, I wish to add that the spawn 

 found by me had "the light violet-gray tint " and crape-like 

 a])pearance he describes. I am very much on the water in 

 harbours frequented by Lophius, but never saw any of this spawn 

 before. 



We found it in a swirl of the tide off Bantry Bay, where the 

 sea was over 40 fathoms deep, and in the midst of innumerable 

 jelly-fish, which seem to congregate wherever the current is most 

 swift. W. S. Green. 



Carrigaline. 



THE '' METEOROLOGISKE INS TI TUT" AT 

 UPSALA, AND CLOUD MEASUREMENTS. 



'in HE Meteorological Institute at Upsala has gained so 

 -*• much fame by the investigations on clouds which 

 have been carried on there during the last few years, that 

 a few notes on a recent visit to that establishment will 

 interest many readers. 



The Institute is not a Government establishment ; it is 

 entirely maintained by the University of Upsala. The 

 personnel consists oi Prof. Hildebrandsson, as Director; 

 M. Ekholm and one other male assistant, besides a lady 

 who does the telegraphic and some of the computing 

 work. 



The main building contains a commodious office, with 

 a small library, and living apartments for the assistant. 

 The principal instrument- room is a se, arate pavilion in 

 the garden. Here is located Thiorell's meteograph, 

 which records automatically every quarter of an hour on 

 a slip of paper the height of the barometer, and the read- 

 ings of the wet and dry thermometers. Another instru- 

 ment records the direction and velocity of the wind. 



This meteograph of Thiorell's is a very remarkable 

 instrument. Every fifteen minntes an apparatus is let 

 loose which causes three wires to descend from rest till 

 they are stopped by reaching the level of the mercury in 

 the different tubes. When contact is made with the 

 surface of the mercuries, an electric current passes and 

 stops the descent of each wire at the proper time. The 

 downward motion of the three wires has actuated three 

 wheels, each of which carries a series of types on its edge, 

 to denote successive readings of its own instrument. For 

 instance, the barometer-wheel carries successive numbers 

 for every five hundredth of a millimetre — 76o"oo, 76o'o5, 

 760' I, &c. ; so that when the motion is stopped the upper- 

 most type gives in figures the actual reading of the baro- 

 meter. Then a subsidiary arrangement first inks the 

 types, then prints them on a slip of paper, and finally 

 winds the dipping wires up to zero again. 



An ingenious apparatus prevents the electricity from 

 sparking when contact is made, so that there is no oxida- 

 tion of the mercury. The mechanism is singularly 

 beautiful, and it is quite fascinating to watch the self- 

 acting starting, stopping, inking, and printing arrangements. 

 We could not but admire the exquisite order in which 

 the whole apparatus was maintained ; the sides of the 

 various glass tubes were as clean as when they were new, 

 and the surfaces of the mercuries were as bright as 

 looking-glasses. 



The University may well be proud that the instruments 



were entirely constructed in Stockholm, by the skilful 

 mechanic Sorrenson, though the cost is necessarily high. 

 The meteograph, with the anemograph, costs /600, but 

 the great advantage is that no assistant is required to sit 

 up at night, and that all the figures wanted for climatic 

 constants are ready tabulated without any further labour. 

 But the Institute is most justly celebrated for the re- 

 searches on the motion and heights of clouds that have 

 been carried on of late years under the guidance of Prof. 

 Hildebrandsson, with the assistance of Messrs. Ekholm 

 and Hagstrom. 



The first studies were on the motion of clouds round 

 cyclones and anticyclones ; but the results are now so well 

 known that we need not do more than mention them here. 

 Latterly the far more difficult subjects of cloud heights 

 and cloud velocities have been taken up, and as the 

 methods employed, and the results that have been ob- 

 tained are both novel and important, we will describe 

 what we saw there. 



We should remark, in the first instance, that the motion 

 of the higher atmosphere is far better studied by clouds 

 than by observations on mountain-tops ; for on the 

 latter the results are always more or less influenced by 

 the local effect of the mountain in deflecting the wind, 

 and forcing it upwards. 



The instrument which they employ to measure the 



Fig. I. — N. F.kholm Measuring Clouds. 



This figure shows the pecu'iar ocular part of the altazimuth, with the 

 vertical and horizontal circles. It also snows the telephonic arrangement. 



angles from which to deduce the height of the clouds is a 

 peculiar form of altazimuth, that was originally designed 

 by Prof. Mohn, of Christiania, for measuring the parallax 

 of the aurora borealis. It resembles an astronomical 

 altazimuth, but instead of a telescope it carries an open 

 tube without any lenses. The portion corresponding to 

 the object-glass is formed by thin cross-wires ; and that 

 corresponding to the eye-piece, by a plate of brass, 

 pierced in the centre by a small circular hole an eighth 

 of an inch in diameter. The tube of the telescope is 

 leplaced by a lattice of brass-work, so as to diminish, as 

 far as possible, the resistance of the wind. The vertical 

 and horizontal circles are divided decimally, and this 

 much facilitates the reduction of the readings. 



The general appearance of the instrument is well shown 

 in the figure, which is engraved from a photograph I took 

 of M. Ekholm while actually engaged in talking through a 

 telephone to M. Hagstrom as to what portion of a cloud 

 should be observed. The lattice-work tube, the cross- 

 wires in place of an object-glass, and the vertical circle 

 are very obvious, while the horizontal circle is so much 

 end on, that it can scarcely be recognized except by the 

 tangent screw which is seen near the lower telephone. 

 Two such instruments are placed at the opposite 



