June 1, 1897.] 



KNOWLEDGE 



139 



satisfied for the present to neglect this element, as 

 Dr. CroU does ; and then the problem will be the 

 following : — Is an equal or an miequal distribution of 

 the total amount of annual heat received at any place 

 more favourable to the formation of a permaiitnt ite-cap ? 



Of course there are regions where considerable quan- 

 tities of snow and ice may now be met with in winter, 

 where, with an equal distribution of the annual heat, 

 there would be no snow or ice at any season. But how is 

 it proved that by any distribution of this total annual 

 heat a permanent ice-cap can be formed in these 

 regions ? — for it is with such permanent ice-caps that we 

 are dealing. The ice-cap, according to Croll, would never 

 be melted if the eccentricity and perihelion did not change. 

 On the other hand, there are probably regions in which, 

 if the total annual heat was uniformly distributed, the 

 ground would never be fi-ee from snow and ice ; whereas 

 the present unequal distribution enables the ground to 

 be cleared and vegetation to grow for a short time 

 during summer. Dr. Croll insists a good deal on the 

 shortness of the summers at the period of maximum 

 eccentricity and winter aphelion ; but how is it proved 

 that a given quantity of heat will produce less effect 

 in melting snow and ice when compressed into a 

 short period than when spread over a long one ? 

 Short as the summers may have been at this period, 

 we received more heat from the sun during them 

 than during the longer summers experienced at present. 

 Why, then, should they not prove more efficacious in 

 melting snow and ice ■? If we received in a single day the 

 entire heat which is now spread over our whole summer, 

 I would expect to find the glaciers and snow-caps reduced 

 to an imprecedented extent on the following morning. It 

 IS said that some volcanic mountains have been cleared of 

 snow in a single day before an eruption. Generally 

 speaking, I think a given quantity of heat will produce the 

 greatest effect when compressed into the shortest time. 

 At all events, it is only when time affects the total 

 quantity of heat that it becomes an important factor in the 

 result. If I am wrong in this, I hope some disciple of Croll 

 will set me right, and show that an amount of heat equiva- 

 lent to a given number of foot pounds will melt more snow 

 when absorbed in twenty-four hours than when absorbed 

 in the same number of minutes, or else that a smaller 

 proportion of it will be reflected without absorption when 

 the time is lengthened. 



Dr. CroU's theory seems likely to be refuted otherwise. 

 The amount of post-glacial erosion is regarded by many 

 geologists as too small to be explained by a glacial period 

 as remote in date as that of Dr. Croll. On this subject I 

 am not competent to offer an opinion, but on reading over 

 the arguments in favour of the theory, I feel surprised 

 that their inconclusiveness has not been more generally 

 recognized. 



The entire subject is too large to be dealt with in a letter 

 like the present, but I do not think Croll has proved either 

 that we would not in the British Islands receive enough 

 heat during each short hot summer to melt the snow and 

 ice formed during the previous winter, or that this heat 

 would be diverted to some other purpose and would leave 

 the snow and ice (or some of it) nnmelted when the next 

 winter came on. 



That the diversion of the Gulf Stream would deprive us 

 of a good deal of heat must be admitted, but I do not 

 think Dr. Croll has proved that it was in fact diverted at 

 this period. Indeed the continuance of the Gulf Stream 

 during the glacial period seems to afford the best explana- 

 tion of the Limits of glaciation on the opposite shores of 

 the Atlantic. W. H. S. Monck, 



YAEIABLE STARS. 

 To the Editors of Knowledoe. 



Snts, — Continuing the maximum of o Ceti, this appa- 

 rition may be placed on any day between 1896, December 

 16th, and 1897, January 10th, and the differences will 

 hardly exceed three steps ; but the star increased a step or 

 two between these dates. My record is as foUows ; — 



1897. Mag. 1807. Mag. 



January 7 ... .. 41 Pebruarv 6 ... .. 5"0 



8, 9 4-3 ., ■ 12 5-3 



11 4-4 ,. 13 3-05 



13 4o „ IG 5-4 



17 4-4 „ 21 ... 5-2 



18,19,20,21,22 4-3 „ 23 50 



25,26,27 ... 4-6 „ 27 ... Very red 



28,29,30,31... 4-7 March 6,7 53 



February 2 47 ,, 10 5-4 



Since the last observation the star, owing to rain and 

 cloudy weather, has been invisible, and another view of it 

 this season is hardly probable. 



From December l-")th to March 10th Mira wavered in 

 light, and much oftener than it changed in colour. Its 

 apparent unsteadiness in Ught may, by those so disposed, 

 be smoothed over or charged to errors of observation, but 

 I incline to believe the fluctuations were real. 



As indicated in KNowLEDrrE for October, a minimum of 

 E Scuti at 7'-5m. was reached on July 26th, and a maximum 

 of 5'4m. followed on August 29th. These phases were in 

 reverse order of production. The succeeding phases were 

 faintly marked, for from August 80th to November 1st the 

 star varied less than a magnitude, but during this interval 

 of two months it was very red. On the latter date it 

 broke away, falling from 0-Om. to 7'Om. on November 8th. 

 After this it was not seen, having passed too far west for 

 observation, but it is reasonable to suppose that it reached 

 a minimum on November 10th, the date given for that 

 phase in the "Companion." 



Verification of this was interesting, as it would show 

 that it had returned to its old elements after being dropped 

 from the Catalogue by Dr. Chandler and the " Companion." 



But E Scuti is now a morning visitor, with which the 

 moon interfered in the last week of January, but I found 

 it near the horizon on the morning of February 2nd. My 

 record since is as follows : — 



showing a maximum in regular order from the old epoch. 



Further observations — imtil E Scuti appears in the 

 evening — are impracticable, as daylight comes on too 

 early. Davu) Flaneby. 



Memphis, Tenn., U.S.A., 

 19th March, 1897. 



€>Jbttiiiirg. 



By the death of Mr. A. D. Bartlett, on the 7th May — a 

 man who could claim acquaintance with all the leading 

 zoologists of his age — visitors to the Zoological Gardens in 

 Eegent's Park will miss a familiar figure and genial 

 superintendent, ever ready to impart information. Mr. 

 Bartlett was born in 1812, and was appointed to his 

 responsible position at the " Zoo " in 18.J9, where he con- 

 tinued to discharge his duties till within a few weeks of 

 his death at the great age of eighty-five years. He was a 

 man of much resource, as well as of immense general 

 knowledge, and his unique experience in the treatment of 

 wild creatures of all kinds in captivity was invaluable to 



