A/aj' ^1, 1877] 



jVA rURE 



S9 



If we take the contra-parallelogram of Mr. Hart and 

 bend the links at the four points which lie on the same 

 straight line, or foci, as they are sometimes termed, 

 through the same angle, the four points, instead of lying 

 in the same straight line, will lie at the four angular points 

 of a parallelogram of constant angles — two the angle that 

 the bars arc bent through, and the other two their supple- 

 ments — and of constant area, so that the product of two 

 adjacent sides is constant. 



In Fig. 16 the lettering is preserved rs in Fig. 12, so 

 that the way in which the apparatus is foimed may be at 

 once seen. The holes are taken in the middle of the 

 links and the bending is through a right angle. The four 

 holes O P O' C lie at the four corners of a right-angled 

 parallelogram, and the product of any t'vo adjacent sides, 

 as for example O C " O P, is constant. It follows that if 

 O be pivoted to the fixed point O in Fig. 16, and C be 

 pivoted to the extremity of the extra link, P will describe 

 a straight line, not P i\I, but one inclined to P M at an 

 angle the same as the bars, are bent through, i.e., a right 

 angle. Thus the straight line will be parallel to the line 

 joining the fixed pivots O and O. This apparatus, which 

 for simplicity I have described as formed of four straight 

 links which are afterwards bent, is of course strictly 

 speaking, formed of four plane links, such as those em- 

 ployed in Fig. I, on which the various points are taken. 

 This explains the name given to it by Prof .Sylvester, the 

 " Ouadruplane." Its properties arc not difficult to inves- 

 tigate, and when I point out to you that in Fig. 16 as in 

 Fig. 12, Ob, /' C form half a '" spear-head," and O <;, a P 

 half a " kite," you will very soon get to the bottom of it. 



I cannot leave this apparatus in which my name is 

 associated with that of Prof. Sylvester without expressmg 

 my deep gratitude for the kind interest which he took in 

 my researches, and my regret that his departure for 

 America to undertake the post of Professor in the new 

 Johns Hopkins University has deprived me of one whose 

 valuable suggestions and encouragement helped me much 

 in my investigations. 



( To be continued^ 



METEOROLOGICAL NOTES 



Notes of the Weather in Scotl.\nd, Faro, and 

 Iceland. — It appears from the meteorological returns for 

 the eight principal towns in Scotland, that the weather 

 of last April has been distinguished by low temperature, 

 3°7 under the average, great fluctuations in the baro- 

 metric pressure, large rainfall distributed among the 

 towns with unusual uniformity, much wind and that more 

 persistently from the eastward than has been before 

 chronicled for any month of any year since the Scottibh 

 Meteorological Society was founded. At the monthly 

 meeting of the Edinburgh Botanical Society, held on 

 Thursday, May 10, Mr. AIcNab stated that the present 

 spring is later than any other during the last twenty-eight 

 years, when systematic observations on the flowering of 

 plants began to be made in the Royal Botanic Garden of 

 Edinburgh. In Faro the winter and early spring have been 

 among the worst ever known, high easterly and northerly 

 winds and snowstorms being very prevalent. In March 

 and April sr.ow fell on no fewer than thirty-one days. The 

 mean barometric pressure at 32° and sea-level at Thors- 

 havn during April, was 29,945 inches. On the other 

 hand the winter, until Easter, was one of the finest ever 

 known in Iceland, particularly in the north of the island. 

 There was little snow, any frost that occurred was of 

 short continuance, and fine calm weather prevailed. But 

 about Easter-day a series of northerly snowstorms began, 

 accompanied by severe frosts, which lasted with little in- 

 termission for about a week, causing the loss of many 

 ships, and snowing up the pastures. Since these storiuj 

 sunshine prevailed up to May 6. When the steamer 



left Reykjavik the Greenland and Spitzbergen ice had ap- 

 peared olf the northern coasts about the middle of March, 

 but only stray icebergs neared the land, the ice becom- 

 ing "land-fast" nowhere in any quantity. The season 

 has also been singularly mild in Canada. Spring 

 set in there fully three weeks earlier than usual, and as 

 very little rain had fallen up to the close of April and the 

 thaw was very gentle, the rivers were unusually low for 

 the time of the year. 



Meteorology of Holland. — A highly-important 

 work on the annual march of the thermometer and baro- 

 meter in Holland, deduced from observations made from 

 1843 to 1875, has been published by Dr. Buys Ballot, the 

 distinguished director of the meteorological system of that 

 countty. The monthly means for each meteorological 

 lustrum of five years, as well as for the whole period 

 during which the observations have been made, are given 

 for each of the hours of observations. From these general 

 averages, the normal values for each of the ten stations 

 have been determined by the process of differentiation, so 

 that the normals, are substantially the averages which 

 would have been obtained if the observations at each of 

 the stations had been made during precisely the same 

 terms cf years. The normals are calcukited for very 

 extended periods by a comparison of the results arrived 

 at for the Dutch stations, with the long averages for 

 Copenhagen, Paris, and Greenwich. Thennometric and 

 barometric normals have also been determined for each 

 day of the year for all the stations, which cannot but 

 prove to be of considerable value in framing forecasts of 

 the weather and in some other practical matters. We 

 hope, however, that Dr. Buys Ballot may be enabled soon 

 to calculate the arithmetic ir;eans of the temperature of 

 each day of the year at all his stations, and thus com- 

 plete what must be regarded as an able and exhaustive 

 discussion of the two most important elements of the 

 meteorology of Holland. Tables are also added, showing 

 the mean temperature of each month during the whole 

 prriod of observations, and an exceedingly valuable table 

 of the monthly mean loarometric measure at Maestricht 

 for sixty-nine years, beginning with 1807 and ending with 

 1875. 



Tycho Brake's Meteorological Journal. — The 

 Royal Academy of Sciences and Letters of Copenhagen 

 has laid scientific men generally under a debt of gratitude 

 in publishing i7t e.xtcnso, the Meteorological Journal, kept 

 at Uraniborg in the Isle of Hveen by Tycho Brahe from 

 1582 to 1597. To the journal is appended a clear and 

 interesting resume of the observations by M. Paul la 

 Cour. The results of the observations made on clouds, 

 rain, snow, hail, fog, winds, frost, thunder, halos, and 

 auroras, by the celebrated astronomer nearly 300 years 

 ago, are compared with similar observations made at 

 Copenhagen and other stations in Denmark in recent 

 years. The results of the dilferent sets of observations 

 are fairly accordant when the difterent positions a.nd 

 times of observing are taken into consideration. The 

 most noteworthy difference is in the monthly curve of 

 thunder, the maximum at Hveen being strongly pro- 

 nounced in June, whereas the recent observations at four- 

 teen stations in different parts of Denmark have the 

 maximum extending equally over June, July, and August 

 — a difference perhaps due to a difterent seasonal distri- 

 bution of thunder in different parts of Denmark. Of the 

 seventy-eight auroras which were noted by Tycho Brahe, 

 seventy-six occurred during the ten years from 1582-1591, 

 and only two during the six years immediately following. 

 From the detailed descriptions given of certain auroras 

 and auroral arches, M. Paul la Co.ir concludes that the 

 magnetic inclination at this observatory during 1584 was 

 somewhere between 72' 25', and 73^ 25'. 



"Atlas Meteorologique" of the Observa'joy of 

 Paris, 1875. — A rapid glance through the Atlas Mvteoro- 



