s 4 



NATURE 



[July 20, 191 1 



can be made thereby zero for any particular latitude 

 in one hemisphere only. There is a second correction 

 due to the ship's motion in latitude, small and inde- 

 pendent of the particular instrument, and there is a 

 third correction, a ballistic correction due to change 

 in the ship's motion in latitude. Space does not admit 

 of these being followed out, but they are fully ex- 

 plained. 



The directive force of the gyrostatic compass is 

 about fifteen times as great as that of an ordinary 

 magnetic compass undisturbed by surrounding iron. 

 In addition, therefore, to its being undisturbed by the 

 magnetism of the ship or the movements of heavy 

 magnetic pieces, such as guns, a master gyrostatic 

 compass may be set up in a protected and quiet spot 

 low down in the ship, and there control a number of 

 dials placed in convenient positions for steering or 

 for taking azimuth observations. These local dials 

 are provided with central dials geared up thirty-six 

 times, so that a complete turn corresponds to ten de- 

 grees. With such a compass to steer by and steering 



Fig. 2. — (t, b, variable outlets for air blast; c, outlet pipe; d. pendulum 

 arm ; e, s, oil cup for gyro bearings ; A ;-, gyro bearings ; ;?, inlet open- 

 ing for air ; </, terminal of gyro motor ; /, gyro case ; o, mercury bowl. 



gear of greater precision than usual, the new compass 

 should effect a saving in the actual distance run and 

 in the horsepower at present wasted on the rudder, 

 and it is an interesting question how long it will take 

 for the reduction in the coal bill to pay for the com- 

 pass. 



It is not possible owing to limitations of space to 

 follow the numerous details relating to the theory, 

 construction, and use of this beautiful instrument, 

 but anvone with a sense of fine mechanics will appre- 

 ciate this excellent exposition, even though he may 

 never have the chance of running the compass him- 

 self. C. V. Boys. 



THE PRESERVATION OF ANCIENT 

 MONUMENTS. 



THE report of the Inspector of Ancient Monuments 

 for the year ending March 31, 1911, is the first 

 by the new inspector, Mr. C. R. Peers. There are 

 in.) monuments under the care of the Commissioners 

 of Works, forty-eight in England and Wales 

 and fifty-seven in Scotland. During the last 

 year fifteen monuments have been placed under 



NO. 2177, VOL. 87] 



the protection of the Ancient Monuments Acts, 

 ten in England and Wales and five in Scot- 

 land. Eight of the newly-protected monuments 

 are situate in Anglesey, all prehistoric monuments, 

 three of which have recently been astronomically sur- 

 veyed by Sir Norman Lockyer and others. Of the 

 two prehistoric Orkney monuments now under pro- 

 tection, the Chambered Mound of Maeshowe has re- 

 ceived the attention of the same authority. 



Useful linear measures are given of the monuments 

 noticed in the report, and in one case, as a sort of 

 nest-egg, we have the information that the bearing 

 of the dolmen at Trefigneth " comes within one degree 

 of the line of the winter solstice." Never a word is 

 found referring to the available astronomical surveys, 

 while it may safely be asserted that the formal pro- 

 tection of the Anglesey and Maeshowe monuments 

 is largely due to the local interest awakened in the 

 astronomical inquiry. In c onnec tion with the state- 

 ment that "no adequate recoTff'has up to the present 

 time been kept of the treatment of each monument 

 year by year," surely the annual reports issued by 

 the Pembrokeshire archaeologists should have been 

 mentioned. 



"Certain observations of a general character" are 

 most timely and important. "The first Ancient Monu- 

 ments Act has now been in operation for twenty-nine 

 years. Of the fifty-one prehistoric monuments scheduled 

 by it as worthy of preservation by the State, twea^y-six 

 have been placed under its provisions, by thecBn^ 

 sent of the owners, while the rest, for various reasons, 

 have not been so placed. In regard to these latter, 

 the position of the State is entirely unsatisfactory, 

 and these monuments are in a worse case than if 

 I hey had not been noticed in the Act." The second 

 Act of 1900 has a wider scope, with the grand result 

 that we have now three castles and three monastic 

 buildings added to the State waifs and strays ! This 

 report, like others of its kind, reveals the deplorable 

 ineffectiveness of high-sounding measures. It also 

 shows that where a scientific survey of a monument 

 is first made and the results dulv published, owners 

 of such properties are among the first to recognise 

 the necessitv for effective protection. Lord Boston, 

 Lord Sheffield, and Major Fox-Pitt have noblv led the 

 way in Anglesey. The first and foremost factor in 

 the case is scientific inspection, and monuments are 

 best preserved in accurate measures. 



John Griffith. 



THE PORTSMOUTH MEETING OF THE 

 BRITISH ASSOCIATION. 



IN about six weeks' time, on August 30, the citizens 

 of Portsmouth will have the privilege of wel- 

 coming the members of the British Association for 

 their annual meeting. In many respects this meeting 

 will be a contrast to that at Sheffield last year. Ports- 

 mouth cannot offer the attractions of large engineer- 

 ing works or manufactories, but at the same time 

 it holds a unique position as the first naval port of the 

 United Kingdom, and one of the most ancient of its 

 boroughs. The borough of Portsmouth fifty or sixty 

 years ago included only a small portion of the island 

 of Portsea, on which the town is situated. There 

 were walls and gates (which were closed every day at 

 sunset) and a military governor. The walls are gone, 

 but some of the old parts of the town are still well 

 win ill a visit. Three years ago the borough boundary 

 was enlarged, now including the whole of the Island 

 of Portsea. 



Opportunity will be offered to members of the 

 British Association to inspect the old corporation plate 

 dating from Queen Elizabeth onward, and the old 

 charters of the town, covering the last 500 years, can 



