53 REPORT — 18G9. 



tliiu steel di-op-piece between the screw and the vacuum-box. All levers, chains, 

 and spiral springs are got rid of, and the vacuum-box has got no work to do in 

 moving the machinery, the required force being supplied by the hand of the 

 observer. In shape and size the Mam-y is precisely like an old-fashioned watch. 

 The outside diameter is 2^ inches, the thickness about f of an inch, the weight 

 from .3 to -Si oz. (3n the dial is a scale ingeniously an-anged in spiral coils, on 

 which a range of 24 barometric inches, equal to 27,000 feet of elevation, can be 

 engraved, with 50 divisions to the inch ; the smallest di-visions, equal to about 20 

 feet, being perfectly leoible to the eye, and large enough for readings to be esti- 

 matfed accurately to 5 teet, and with care and practice almost to a single foot. 

 Various experimeuts were referred to, in which the Mauiy had been tested against 

 the aneroid, and found to be more regular and accurate. 



A plan, suggested by Captain Maury, was also described by which two travellers, 

 each carrying a Maury barometer, and following each other at definite intervals of 

 time and space, could make a very rapid survey over any extent of country, cor- 

 recting each other for all changes of general atmospheric pressure. In conclusion, 

 the author said that the inventor of the Maury barometer claimed for his instru- 

 ment a general superiority over the aneroid in the ratio of 4 to 1 ; and that the ex- 

 periments and compaiisons which had been described not only confirmed that claim, 

 but showed a much larger ratio of advantage. 



Dr. BuBDON Sanderson, F.R.S., exhibited an instrument for recording respi- 

 ratory movements, for a description of which see Section D. 



On a Self-recording Rain-gauge. By Dr. Balfotte Stewart, F.R.S. 



The instrument described in this paper, and which was exhibited to the Meeting, 

 was invented bv Mr. Robert Beckley, of the Kew Observatory, and made and patented 

 by Mr. James tlicks, of Hatton Garden, London. 



It is designed to register the fall of rain by means of the varying immersion of 

 a float in a fluid, and consists of a vessel supported on an annidar plunger resting 

 on a cistern of mercury, into which the rain collected in a funnel is conducted. 



A pencil is fixed to the vessel, and in its descent traces a curve on a cylinder 

 which is moved round regvdarty by a clock. A siphon of peculiar construction is 

 adapted to the receiver, so as to empty it immediately it becomes filled to a certain 

 height. 



In the instrument exhibited the funnel, receiver, and float were so proportioned 

 that a fall of 0-25 inch of rain traced a line I inch long on the cylinder. 



The recording-cylinder is made of imgiazed eartlienware, and the whole of the 

 clock-mechanism employed to give rotation to the cylinder is enclosed in an air- 

 tight case, to protect it from the same injuiy by moistm"e,the motion being trans- 

 mitted by mercurial stuffing-boxes. 



The whole apparatus is contained compactly in a cast-iron case, 14 inches square 

 and 10 high, and can be placed on the gTound or elsewhere without any special 

 arrangements being made for its erection. 



On Collimators for adjusting Newtonian Telescopes. 

 By G. Johnstone Stonet, M.A., F.R.S. 

 The author of this communication hnd described in I8o0, at the Cheltenham 

 Meeting of the British Association, a collimator for adjusting Newtonian telescopes. 

 The collimator resembles a small refracting telescope, with e^'epiece and cross- 

 wires, ditt'eriug from it only in the position of its object-glass, which is to be 

 pushed somewhat in, so that the light transmitted from the illuminated cross-wires 

 may leave the collimator as a divergent beam. To use this collimator, it is to be 

 substituted for the eyepiece of the telescope ; its construction then enables the 

 rays emitted from its illuminated cross-wires to reach the great speculum of the 

 telescope normally, so that, after reflection by tlie speculum, tliey return upon their 

 path and form an image, which, if the great telescope be in adjustment, coincides 

 with tlie cross-wires. 



