October 30, 1914] 



SCIENCE 



637 



from protozoan cell to highest vertehrate in 

 the course of geologic ages, he let 40 weeks 

 (reduced to hours) represent geologic time — 

 say 20 or 40 million years. For the third 

 term in the proportion he took the number of 

 hours it was necessary to observe the embryonic 

 development in order to detect an apprecia- 

 ble change, and obtained for an answer as the 

 fourth term a number in years which was 

 much longer, even when the shortest lengths 

 of geologic time were taken, than our his- 

 toric period. 



So that it was clear there was plenty of 

 geologic time for evolution to proceed at a 

 pace so slow that it could not be detected 

 within the historic period and still accomplish 

 its perfect work. 



When it comes to attempts to estimate geo- 

 logic time in years it seems to me that most 

 persons must agree that they are not very 

 satisfactory. This is particularly so with those 

 of the physicists who have assumed as a basis 

 for their calculations an origin for our planet, 

 no longer looked upon with much favor in the 

 light of the facts which support the planetes- 

 imal hypothesis. These calculations have 

 also been largely invalidated by discoveries 

 relating to the radio-activity of matter. 



Of all geologic time estimates, those based 

 upon rate of denudation, and its correlative — 

 the rate of deposition of stratified rocks, seem 

 least unsatisfactory. When these methods are 

 applied to precambrian time it is admitted 

 they amount to little more than wild guesses. 



And yet we know that evolution was well 

 on its way before the beginning of Cambrian 

 time. 



Walcott has brought to light in the Cana- 

 dian Eockies abundant evidence of a rich and 

 by no means lowly organized marine fauna at 

 the very beginning of Cambrian time. 



He and others estimate that at least 90 per 

 cent, of the total evolution to the present had 

 taken place before the Cambrian period. 



Le Conte, even before he had had the benefit 

 of these discoveries, was impressed with the 

 high type of the Cambrian faunas. 



His memorable words in this connection are : 



When the curtain goes up on geological history 



at the beginning of the Cambrian Period we find 

 practically all the subkiugdoms of the animal 

 kingdom present and ready to answer to the roll 

 call. 



In the light of these facts what vistas of 

 practically unrecorded geologic time filled with 

 evolutionary process are opened up to us! 



Bold indeed is he who from a rate of devel- 

 opment predicated upon that observed during 

 the brief span of the historic period would 

 assert that geologic time is too short for a 

 gradual evolutionary process. 



Arthur M. Miller 



State University, 

 Lexington, Ky. 



potassium cyanide as an insecticide 

 Reading the article of Professor Fernando 

 Sanford in the October 9 issue, I would add 

 that I have found potassium cyanide very ef- 

 fectual in killing ants in lawns, and it does its 

 work without killing the grass. A half ounce 

 in 6 to 8 quarts of water applied with a 

 sprinkling pot is enough for a nest 18 or 20 

 inches across. 



W. G. Blish 



SCIENTIFIC BOOKS 

 Dialogues concerning Two New Sciences. By 

 Galileo Galilei. Translated from the 

 Italian and Latin into English by Henry 

 Crew and Alfonso de Salvio, of North- 

 western University, with an introduction by 

 Antonio Favaro, of the University of Padua. 

 New York, The Macmillan Company. 1914. 

 Pp. xxi ■+ 300. Price $2.00 net. 

 In these dialogues Galileo presents the re- 

 sults of his investigations in mechanics and 

 physics. His representative, Salviati, speak- 

 ing either for himself or as the reader and 

 expositor of the manuscript of a certain un- 

 named academician — of course Galileo once 

 again — is the principal speaker, and the source 

 of most of the valuable original ideas. 

 Sagredo, the more learned of the other two 

 interlocutors, occasionally contributes some- 

 thing of importance. Simplicio, as an inter- 

 ested layman, raises the objections which 

 would occur to such a man, and gives occa- 

 sion for .the introduction of alternative ex- 



