i6o 



HARDWICKE'S SCIENCE-GOSSIP. 



its victim, leaving nothing but the empty skin. 

 The larva then commences to spin a flask-shaped 

 silken cocoon attached by one end to its support 

 (generally the under -side of a cinchona leaf). It 



through the pipes previous to observing, so as to cool 

 them very quickly. From personal experience I can 

 say that if the hot-water pipes are used of course 

 only for the purpose of drying the observatory, that 

 although cold water may be run through 

 the tubes, it will not be possible to use 

 the telescope for observing for several 

 hours afterwards. A difference of tem- 

 perature of one or two degrees will be 

 sufficient to set up tube currents, which, 

 in so large an aperture will destroy all 

 definition. The heating contrivance 

 may be beneficial to the telescope, but 

 will be of no other service to the 

 observer. 



Mr. Cowper Ranyard describes a 

 contrivance for applying electrical con- 

 trol to the driving clock of an equatorial 

 by making use of the instantaneous 

 current from a pendulum as it passes 

 through a drop of mercury at the 

 bottom of its arc to move a small 

 lever which shifts a little weight from 

 one side to the other of the fulcrum of 

 the clutch which embraces the revolving 

 disc of the governor. The current 

 passes through an insulated revolving 



Fig. 72. — Imago, magnified. Colour black ; a reddish patch upon the thorax ; wheel. When the clock IS fast as 



scutellum and attachment of wings yellowish. Antennae multiarticulate, basal 1 •.! t r,_ ^on/lnlum thp> 



joint reddish. Legs yellowish, tarsi of third pair and terminal joint of first Compared With the pendulum, VOS. 



and second pairs blackish. Wings covered with minute hairs. Segments of current is sent through a horseshoe 

 abdomen with symmetrical rounded prominences. 



builds up the cocoon gradually, completing the 

 walls as it proceeds, forming first a cup-shaped 

 receptacle, which is lengthened by regular additions 

 to the open edge, and finally closed. A specimen 

 under observation completed its work in forty-eight 

 hours. E. Ernest Green. 



Pundiiloya, Ceylon. 



A 



ASTRONOMY AND METEOROLOGY. 



By John Browning, F.R.A.S. 

 T the meeting of the Royal Astronomical Society, 



held on May nth, Mr. E. Crossley gave an 

 account of a large dome he had built and erected at 

 Halifax to protect a reflecting telescope thirty-seven 

 inches in diameter. The dome is thirty-nine feet in 

 diameter, and runs by means of fourteen wheels in a 

 circular iron ring placed on a wall fifteen inches thick. 

 The dome is provided with twenty-three iron ribs. 

 The observer stands in a gallery which moves round 

 with the dome. The dome weighs about fourteen 

 tons. Both the dome, the gallery, and the staircase 

 attached to it, weighing altogether sixteen tons, are 

 moved by a small hydraulic engine placed in a room 

 at the side of the observatory. There are hot-water 

 pipes in the observatory, by means of which it can be 

 warmed in cold weather. Cold water can be run 



magnet on one side of the lever, and 

 when it is slow through a similar magnet on the 

 other side of the lever. This shifts the weight, and 

 increases or decreases the pressure on the revolving 

 governor disc. When the clock is [keeping time, the. 

 weight is drawn to the central position by a third 

 magnet. 



On July 23rd there will be a total eclipse of the 

 moon partially visible at Greenwich. The first 

 contact with the shadow takes place at 3 hrs. 55 m. 

 in the morning. The total phase begins at 4 hrs. 

 54 m. morn., and ends at 6 hrs. 36 m., the last 

 contact with the shadow will be at 7 hrs. 35 m. The 

 moon sets at 4 hrs. 10 m., about 44 minutes before 

 the total phase commences. 



There will be no occultation of any star above the 

 4th mag. in July. 



Mercury will be very near the sun until the middle 

 of the month, afterwards it will be a morning star. 



Venus will rise and set with the sun. 



Mars will be in Virgo, near to Spica at the 

 beginning of the month. 



Jupiter will be in Libra in conjunction with the 

 moon on the iSth at 5 hrs. aft. 



Saturn will be an evening star in conjunction with 

 the moon at 8 hrs. aft. on the loth. 



Meteorology.— At the Royal Observatory, Green- 

 wich, the highest reading of the barometer for the 

 week ending 19th of May was 30-20 in. at the 



