May 13, ]R9a.] 



SCmNGE. 



683 



were more plastic than those that had been 

 longer established ; he mentioned several cases 

 among shells and birds that could with diffi- 

 culty be considered by mathematical tests. 



Dr. R. T. Jackson alluded to cases among 

 shells showing a radical diflference in the right 

 and left sides and to radial variations showing 

 differentiation in a single individual. 



Professor Alpheus Hyatt considered that in 

 the papers of Dr. Davenport and Mr. Blankin- 

 ship opinion was largely replaced by a definite, 

 exact method which should be thoroughly 

 tested. Its applicability would seem confined 

 to characters that can be measured. He 

 doubted if the color characters of the Achati- 

 nelliuEe could be expressed in numbers. 



Samuel Henshaw, 



Secretary. 



NEW YORK ACADEMY OF SCIENCES — SECTION 



OP GEOLOGY AND MINERALOGY, 



APRIL IS, 1898 . 



The first paper of the evening was by Dr. A. 

 A. Julien on the ' Elements of Strength and 

 Weakness in Building Stones. ' Dr. Julien called 

 attention to the fact that in the testing of build- 

 ing stones little consideration is given to the 

 causes influencing their variovis properties. In 

 judging the resistance which a stone shows to- 

 wards weathering, care should be taken to 

 recognize the character of the forces to which 

 it has been subjected. The strength of a stone 

 bears no relation to its mineral components, 

 but is dependent on the shape and arrangement 

 of the mineral grains and the character of the 

 cementing material. In considering the strength 

 of a stone four facts have to be kept in mind, 

 viz : interlockment of the particles ; coherence, 

 dependent on character of the cement and ad- 

 hesion of the grains ; rigidity; and tension. 



The ' quarry sap ' he believes, plays a more 

 important role than has hitherto been recog- 

 nized, as it probably carries much of the cement 

 in solution and deposits it only when the stone 

 is exposed to the air. This accounts for the 

 hardening of the stones after being quarried. A 

 distinction should also be made between po- 

 rosity due to cavities between the grains and in- 

 terstices in the individual minerals. The former 

 is a source of weakness, the latter not, although 



either may cause the rock to exhibit a high ab- 

 sorptive capacity. 



All these points, which have important bear- 

 ing on the strength of building stones, are best 

 studied with the microscope. The paper was 

 illustrated by means of sections thrown on the 

 screen with a polarizing lantern. Discussion 

 was by Professor Kemp and Mrs. Dudley. 



The second paper of the evening was by J. 

 D. Irving on ' Contact-metamorphism of the 

 Palisades Diabase. ' Mr. Irving referred to the 

 work done by Professors Osann and Andrae 

 some years ago and stated that his results agreed 

 with theirs, but recent railroad excavations at 

 Shadyside had enabled him to obtain additional 

 facts. The diabase flow becomes denser, finer 

 grained and prophyritic towards the contact 

 with a decrease in hypersthene. It is also 

 conformable to the Newark shales. In addition 

 to the zones found by Osann, Mr. Irving found : 

 1. A normal hornfels zone rich in spinel ; 2. a 

 hornfels zone with brown basaltic hornblende 

 layers ; 3. hornfels with an undeterminable 

 isotropic mineral resembling leucite ; 4. horn- 

 fels with andalusite becoming more arkose far- 

 ther from the contact. The diabase is to be 

 considered as an intruded mass and not a sur- 

 face flow. The paper was discussed by Profes- 

 sors Kemp and Dodge, and Dr. Hovey and Mr. 

 White. Heinrich Hies, 



Secretary of Section. 



CHEMICAL SOCIETY OP WASHINGTON. 



The regular monthly meeting was held on 

 March 10, 1898. 



Dr. E. A. de Schweinitz presented a paper on 

 ' The Pasteur Milk Laboratory of Washington. ' 

 The speaker first reviewed briefly some of the 

 ways in which milk can become infected, either 

 from the fact that the animals are dirty and the 

 stables in a filthy condition, or from the care- 

 lessness of the milkers, the dirty condition of 

 the pans and pails and the use of impure water 

 for washing these utensils. Attention was also 

 called to the fact that dogs, cats, rats, mice, 

 etc., which often obtain access to the place 

 where the milk is ordinarily kept in the country, 

 may afiect the milk, as it is well known that 

 these animals are often carriers of disease. In 

 view of all these well known dangers, and es- 



